evaluate a squared - 3a +2ab - 6b for a = -3 and b=2

Question

this is for college placement testing just cant figure how they end with -6 for an answer

Answer 1

a^2 -3a +2ab -6b at a=-3 & b=2

9 -3*(-3) +2*(-3)*2 -6*2

9 +9 -12-12

=18 -24

=-6

Answer 2

if a = -3 and b = 7, find -2ab