4(y-9)=(y+21)

Solution for 4(y-9)=(y+21) equation:

Simplifying
4(y + -9) = (y + 21)

Reorder the terms:
4(-9 + y) = (y + 21)
(-9 * 4 + y * 4) = (y + 21)
(-36 + 4y) = (y + 21)

Reorder the terms:
-36 + 4y = (21 + y)

Remove parenthesis around (21 + y)
-36 + 4y = 21 + y

Solving
-36 + 4y = 21 + 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.
-36 + 4y + -1y = 21 + y + -1y

Combine like terms: 4y + -1y = 3y
-36 + 3y = 21 + y + -1y

Combine like terms: y + -1y = 0
-36 + 3y = 21 + 0
-36 + 3y = 21

Add '36' to each side of the equation.
-36 + 36 + 3y = 21 + 36

Combine like terms: -36 + 36 = 0
0 + 3y = 21 + 36
3y = 21 + 36

Combine like terms: 21 + 36 = 57
3y = 57

Divide each side by '3'.
y = 19

Simplifying
y = 19