What is the ratio of a:b, knowing that (a-b)/(a+b)=3/5
(a - b) / (a + b) = 3 /5 cross-multiply
3 (a + b) = 5 (a - b)
3a + 3b = 5a - 5b
3b + 5b = 5a - 3a
8b = 2a
4b = a
a / b = 4
