if the same number is added to numerator and denominator of 5/8, the result is equal to 5/6. Find the number.

Question

please help me if I don't get this I will fail my second semester 

 

Answer 1

(5+x)/(8+x)=5/6

6(5+x)=5(8+x)

x=10

Check: 15/18=5/6