Question

a:b=5:3,find 5a-3b/5a+3b

Answer 1

Multiplying both sides by 5*3, we get 5a:3b=25:9. Then by componendo and dividendo, 5a+3b/5a-3b=34/16. Divide it by 1. The answer is 16/34=8/17.

Answer 2

a : b = 5 : 3
a = 5b/3

(5a - 3b) / (5a + 3b)
= (5 . 5b/3 - 3b) / (5 . 5b/3 + 3b)
= (25b - 9b)/3 : (25b + 9b)/3
= 16b/34b
= 8/17