Question

-3(2-b)+3а, если a+b=2

Answer 1

$-3(2-b)+3a= \\= -6+3b+3a =\\=-6+3(b+a) \\ \\a+b= 2 \\ \\ -6+3*2=-6+6=0$

Answer 2

-6+3b+3a =-6+6=0
   a+b=2    3a+3b=2*3=6