Ernise evaluated the expression 10(3 + 5) like this:
step 1: 10.3 + 10.5
step 2: 30 + 50
step 3: 80
which mathematical property was she using?

distributive property

Dist. can be identified by x(y+z)

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