For the first one, you would just multiply everything left-to-right. -8 x 9 x 2 = -144. For the second one, since there are different variables, you can't combine them to get just a number. Multiply 3a by -6b to get -18ab, and then multiply that by -4 to get 72ab (the number is positive because when you multiply two negative numbers, you get a positive number).
