What is three twelves minus four tens?

Answer 1

(3 * 12) - (4 * 10) = 36 - 40 = -40 + 36 = -(40 - 36) = -4

It may make it easier for you to do it this way:

Subtract the smaller number from the biggest (40 - 36 = 4)

Keep the sign of the bigger number (-4)