Find the measure of angle A

21 degrees

Step-by-step explanation:

Triangles have a total angle of 180 degrees.

This makes our equation:

3x+3+4x+135=180

Subtract 135 from both sides and combine like terms

7x + 3 = 45

Subtract 3 from both sides

7x = 42

Divide both sides by 7

x = 6

Plugging the number in:

3x + 3 =

3(6) + 3 =

21

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