Answer: 28
-9^2 - (-6)^2 + 3 - 20
so follow order of operations
P = parentheses
E = exponents
D = divide
M = multiply
A = add
S = subtract
since there are no parentheses, do exponents
-9^2 = 81
-6^2 = 36
so now its
81 - 36 + 3 - 20
now follow order of operations
81 - 36 = 45
45 + 3 - 20
3 - 20 = -17
45 + -17 = 28
so your answer is 28