Simply
3Y+-21=12X
Re-order the terms
-21+3Y=12X
(Solving for Y variable)
Move all terms containing y to the left, all other terms to the right.
Add 21 to each side of the equation
-21+21+3Y=21+12X
Combine like terms: -21+21=0
0+3Y=21+12X
3Y=21+12X
Divide each side by 3
Y=7+4X
Simplifying
Y=7+4x
I hope this helps!! :)
