2. Which example does NOT show the commutative property of addition?
A. 4 + x = x + 4
B. ab = ba

C. a+b = b + a
D. 3x + 4y = 4y + 3x

I think it would be b.ab=ba but I'm, not 100% sure

Step-by-step explanation:

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18