Question

The fraction that's equivalent to 6/7. The sum of the numerator and the denominator is 78. What is the fraction?

Answer 1

6*6= 36
7*6- 42

36+42= 78. 

The fraction is 36/42.

Answer 2

Let x be the factor that both the numerator and denominator are multiplied by to have an equivalent fraction.

so 6x/7x is 6/7

then
6x+7x=78
13x=78
x=78/13
x=6

therefore the fraction is (6*6)/(7*6) or 36/42

check: 36+42=78 !