You have to evaluate both sides of the expression to see which comparison operator applies.
Left side: 3·12 -12 = 36 -12 = 24
Right side: 3·(26 -2·(3 +6)) = 3·(26 - 2·9) = 3·(26 -18) = 3·8 = 24
The appropriate choice is "=" since the two sides have the same value.