You must learn to substitute:
2x-3y=16 where x=3y+11
Replace the x in the first equation by what x equals in the
second equation, 3y+11, placed in parentheses (3y+11):
2(3y+11)-3y=16
Distribute to remove the parentheses
6y+22-3y=16
Combine the two like terms on the left 6y and -3y, getting 3y
3y+22=16
Add -22 to both sides
3y+22=16
-22=-22
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3y =-6
Divide both sides by 3
Now substitute (2) for y in
x=3y+11
x=3(-2)+11
x=-6+11
x=5
Edwin