5m + 9n if m = -7 and n = 4

x² - xy if x = 8 and y = -3

(18 - ab) + 4b if a = -2 and b = -5

-7w² + 2w if w = -4

12x ÷ 4y if x = -8 and y = 3

(20ab) ÷ (a-b)² if a = 4 and b = -2

8(9) - (2 + 4)³