Answer:
x=-2
y=9
Step-by-step explanation:
3=y+3x ---- A
-x+3y=29 ----B
step 1. rearrange equation A, so you have the "y" variable on one side
3=y+3x
-3x -3x
3-3x=y
y=3-3x ---- C
step 2. Substitute equation C into equation B in place of "y"
-x+3(3-3x)=29 ---foil
-x+9-9x=29 -- collect like terms
-10x+9=29
-9 -9
-10x=20
÷-10 ÷-10
x=-2
Step 3. Substitute x=-2 into equation C to find y
y=3-3(-2)
y=3+6
y=9
Check you answer by subsituting x=-2 and y=9 back into equation A and B
