If a number is added to the numerator of 5/7 and the same number is subtracted from the denominator, the result is 3. Find the number.

Question

If a number is added to the numerator of
5
7
and the same number is subtracted from the denominator, the result is 3. Find the number.

Answer 1

To write this algebraically, let x = the unknown number. Then we have:

 

(x + 5)/(7 - x) = 3

 

Cross multiply to get:

 

3 (7 - x) = x + 5

21 - 3x = x + 5

16 = 4x

4 = x

 

The unknown number is 4