3(y+5)-21=0

Solution for 3(y+5)-21=0 equation:

Simplifying
3(y + 5) + -21 = 0

Reorder the terms:
3(5 + y) + -21 = 0
(5 * 3 + y * 3) + -21 = 0
(15 + 3y) + -21 = 0

Reorder the terms:
15 + -21 + 3y = 0

Combine like terms: 15 + -21 = -6
-6 + 3y = 0

Solving
-6 + 3y = 0

Solving for variable 'y'.

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

Add '6' to each side of the equation.
-6 + 6 + 3y = 0 + 6

Combine like terms: -6 + 6 = 0
0 + 3y = 0 + 6
3y = 0 + 6

Combine like terms: 0 + 6 = 6
3y = 6

Divide each side by '3'.
y = 2

Simplifying
y = 2