求出将给定比例a：b加到a：b后比例变为c：d的数字

给定四个整数a ， b ， c和d 。任务是找到数字X ，将其与数字a和b相加后，其比率将从a：b变为c：d 。
例子：

Input: a = 3, b = 6, c = 3, d = 4 
Output: 6 
When 6 is added to a and b 
a = 3 + 6 = 9 
b = 6 + 6 = 12 
And, the new ratio will be 9 : 12 = 3 : 4
Input: a = 2, b = 3, c = 4, d = 5 
Output: 2 
 

方法：旧比例为a：b ，新比例为c：d 。令所需的数字为X ，
因此， (a + X)/(b + X)= c / d
或者，ad + dx = bc + cx
或者，x(d – c)= bc –广告
因此， x =(bc – ad)/(d – c)
下面是上述方法的实现：

C++

// C++ implementation of the approach
#include 
using namespace std;
 
// Function to return the
// required number X
int getX(int a, int b, int c, int d)
{
    int X = (b * c - a * d) / (d - c);
    return X;
}
 
// Driver code
int main()
{
    int a = 2, b = 3, c = 4, d = 5;
 
    cout << getX(a, b, c, d);
 
    return 0;
}

Java

// Java implementation of the approach
import java.io.*;
 
class GFG
{
     
// Function to return the
// required number X
static int getX(int a, int b, int c, int d)
{
    int X = (b * c - a * d) / (d - c);
    return X;
}
 
// Driver code
public static void main (String[] args)
{
 
    int a = 2, b = 3, c = 4, d = 5;
    System.out.println (getX(a, b, c, d));
 
}
}
 
// The code is contributed by ajit..@23

Python

# Python3 implementation of the approach
 
# Function to return the
# required number X
def getX(a, b, c, d):
 
    X = (b * c - a * d) // (d - c)
    return X
 
# Driver code
 
a = 2
b = 3
c = 4
d = 5
 
print(getX(a, b, c, d))
 
# This code is contributed by mohit kumar 29

C#

// C# implementation of the approach
using System;
 
class GFG
{
     
// Function to return the
// required number X
static int getX(int a, int b, int c, int d)
{
    int X = (b * c - a * d) / (d - c);
    return X;
}
 
// Driver code
static public void Main ()
{
    int a = 2, b = 3, c = 4, d = 5;
    Console.Write(getX(a, b, c, d));
}
}
 
// The code is contributed by Tushil.

Javascript

// javascript implementation of the approach
   
// Function to return the
// required number X
function getX(a , b , c , d)
{
    var X = (b * c - a * d) / (d - c);
    return X;
}
 
// Driver code
 
var a = 2, b = 3, c = 4, d = 5;
document.write(getX(a, b, c, d));
 
// This code is contributed by 29AjayKumar

输出：

2