Question

3a-5b=5, a/a+b=5/7, then(a-b)=?

Answer 1

As we have two eqns, first is  3a - 5b = 5  --- (1) 
and second is                a/a+b = 5/7
                                      7a = 5(a + b)
                                   or 2a - 5b = 0  ----- (2)
therefore, subtracting 1 and 2 we will get a = 5 and b = 2 
 and (a-b) = (5-2) = 3 Ans.

Answer 2

3a-5b=5
2a-5b=0 by solving a/a+b=5/7
by elimination method
a=5 and b=5
a-b=5-2=3