Solve the system of equations using substitution. 3y = –1/2x + 2 y = –x + 9

For the given equations, (x,y)=(10,−1)

[1]3y=−12x+2
[2]y=−x+9

While it is not technically necessary, I find it easier to clear the fractions before actually beginning; so multiplying [1] by 2
[3]6y=−x+4

Substituting (from [2]) (−x+9) for y in [3]
[4]6(−x+9)=−x+4

Simplifying
[5]−6x+54=−x+4
[6]5x=50
[7]=10

Substituting (from [7]) 10 for x in [2]
[8]y=−10+9=−1