Solve by the substitution method?

Question

2x + 9y = 33
-2x + y = 17

Answer 1

2x + 9y = 33
-2x + y = 17 ---------> y = 2x+17
substitute y = 2x+17 in 2x + 9y = 33
2x + 9(2x+17) = 33
2x + 18x + 153 = 33
20x + 153 = 33
subtract 153 from each side
20x + 153 -153 = 33 -153
20x = -120
divide each side by 20
20x/20 = 120/20.
x=-6
substitute x=-6 in -2x + y = 17
-2 *- 6 + y = 17
y = 17 - 12 = 5
(x , y) =(-6, 5)

Answer 2

substitute y = 2x+17 in 2x + 9y = 33
2x + 9(2x+17) = 33
2x + 18x + 153 = 33
20x + 153 = 33    (subtract 153 from each side)
20x + 153 -153 = 33 -153
20x = -120           (divide each side by 20)
20x/20 = 120/20.
x=-6
substitute x=-6 in -2x + y = 17
-2 *- 6 + y = 17
y = 17 - 12 = 5
(x , y) =(-6, 5)

solution to the system of eqution 2x + 9y = 33 , -2x + y = 17 is  (-6,5)