(9y+6)+(21y-6)=90

Solution for (9y+6)+(21y-6)=90 equation:

Simplifying
(9y + 6) + (21y + -6) = 90

Reorder the terms:
(6 + 9y) + (21y + -6) = 90

Remove parenthesis around (6 + 9y)
6 + 9y + (21y + -6) = 90

Reorder the terms:
6 + 9y + (-6 + 21y) = 90

Remove parenthesis around (-6 + 21y)
6 + 9y + -6 + 21y = 90

Reorder the terms:
6 + -6 + 9y + 21y = 90

Combine like terms: 6 + -6 = 0
0 + 9y + 21y = 90
9y + 21y = 90

Combine like terms: 9y + 21y = 30y
30y = 90

Solving
30y = 90

Solving for variable 'y'.

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

Divide each side by '30'.
y = 3

Simplifying
y = 3