12-9=y+3

Solution for 12-9=y+3 equation:

Simplifying
12 + -9 = y + 3

Combine like terms: 12 + -9 = 3
3 = y + 3

Reorder the terms:
3 = 3 + y

Add '-3' to each side of the equation.
3 + -3 = 3 + -3 + y

Combine like terms: 3 + -3 = 0
0 = 3 + -3 + y

Combine like terms: 3 + -3 = 0
0 = 0 + y
0 = y

Solving
0 = y

Solving for variable 'y'.

Move all terms containing y to the left, all other terms to the right.

Add '-1y' to each side of the equation.
0 + -1y = y + -1y
Remove the zero:
-1y = y + -1y

Combine like terms: y + -1y = 0
-1y = 0

Divide each side by '-1'.
y = 0

Simplifying
y = 0