To estimate, you should round some of the numbers to the closest number (rounding up or down). It will be more accurate the less you round. In this problem, we should round -5 1/4 to -5 since it is the closest. -5*-3/2 = 7.7. You will end up with -3/2x (-5 1/4) ≈ 7.5x
≈ means approximately equal.