15. Alexis wrote 28 -8 -20. Then she wrote 28 -8+20 + q. Which property of equality justifies that the equations are equivalent? please don't attack a link here just put the answer please ty bye​

how is that middle school

step-by-step explanation:

she will most likely have 33  

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