-21=3(y+1)

Solution for -21=3(y+1) equation:

Simplifying
-21 = 3(y + 1)

Reorder the terms:
-21 = 3(1 + y)
-21 = (1 * 3 + y * 3)
-21 = (3 + 3y)

Solving
-21 = 3 + 3y

Solving for variable 'y'.

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

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

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

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

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

Combine like terms: 3 + 21 = 24
-3y = 24

Divide each side by '-3'.
y = -8

Simplifying
y = -8