Android Studio displaying numbers and math actions

MainActivity.java :

package com.example.marek.przelicznikpaliw;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void onButtonClick(View v){
        //pola
        EditText a1 = (EditText) findViewById(R.id.cel);
        EditText b1 = (EditText) findViewById(R.id.pali);
        EditText c1 = (EditText) findViewById(R.id.litr);
        EditText d1 = (EditText) findViewById(R.id.koszt);

        // wynik
        TextView tv = (TextView) findViewById(R.id.wynikKoszt);
        TextView tv2 = (TextView) findViewById(R.id.wynikKilometry);

        float a,b,c,d,wynik;
        a = Float.parseFloat(a1.getText().toString());
        b = Float.parseFloat(b1.getText().toString());
        c = Float.parseFloat(c1.getText().toString());
        d = Float.parseFloat(d1.getText().toString());
        wynik = 0;
        if (v.getId() == R.id.button) {
            wynik = ((b / 100) * a)*c;
        } else if (v.getId() == R.id.button2) {
            wynik = d/((b * c) / 100);
        }
        tv.setText(wynik+"");
        tv2.setText(wynik+"");
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

activity_main.xml :

<LinearLayout xmlns:android="http://ift.tt/nIICcg"
    xmlns:tools="http://ift.tt/LrGmb4" android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity"
    android:orientation="vertical"
    android:onClick="onButtonClick">
    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/cel"
        android:hint="Ilosc km do celu to:"
        android:layout_centerHorizontal="true" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/pali"
        android:hint="Ile litrow pali na 100km"
        android:layout_centerHorizontal="true"
        android:layout_below="@+id/cel" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/litr"
        android:hint="Cena za litr"
        android:layout_below="@+id/pali"
        android:layout_centerHorizontal="true" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/button"
        android:layout_below="@+id/litr"
        android:layout_centerHorizontal="true"
        android:hint="Licz zlotowki"
        android:text="Licz koszty"
        android:clickable="true" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/koszt"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true"
        android:hint="Za ile zl zostalo zatankowane gaz/paliwo?" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Licz kilometry"
        android:id="@+id/button2"
        android:layout_below="@+id/koszt"
        android:layout_centerHorizontal="true"
        android:clickable="true" />

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="@string/emptystring"
        android:id="@+id/wynikKoszt"
        android:textIsSelectable="true" />

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="@string/emptystring"
        android:id="@+id/wynikKilometry" />
</LinearLayout>

tv and tv2 should display an math algoritm writen in "if" statement. Can someone help me solve this problem? this should do ((b/100)*a)c when button is clicked and display the math action in tv, and it should do d/((bc)/100) when button2 is clicked and display it in tv2.