Question

a(3b-1)-b(a-3)-2(ab-a+b)

Answer 1

$a left( 3 b-1 right) -b left( a-3 right) -2 left( a b-a+b right) =$

$= a 3 b+a left( -1 right) -b a+3 b-2 a b+2 a-2 b=$

$= a left( -1 right) +b+2 a= a+b$

Answer 2

3ab - a - ba + 3b + 2ab + 2a - 2b= a + b