numerator = x
denominator = x+8
so, numerator is increased by 17 and denominator decreased by 1.
x+17 / x+8-1 = 3/2
x+17 / x+7 = 3/2
(now, cross multiply)
3(x+7) = 2(x+17)
3x + (3*7) = 2x + (2*17)
3x + 21 = 2x + 34
3x - 2x = 34 - 21
x = 13
therefore, the rational number is 13/20