Question

a,b,c are positive integers such that a:b=7:9 and b:c=12:7. What is the smallest possible value of a?

Answer 1

b/c = 12/7, 24/14, 36/21...
a/b = 7/9, 14/18, 21/27, 28/36...

So if there is 28 'a' and 36 'b' we have 7:9 a:b also there is 36:21=b:c=12:7.