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