Question

If it is known that a+b/a-b=c, find the following: 2a-2b/5a+5b

Answer 1

if (a+b)/(a-b)=c, then (a-b)/(a+b)=1/c
(2a-2b)/(5a+5b)=2(a-b)/5(a+b)=2/5 *1/c=2/(5c)