9a+123=21a-21

Solution for 9a+123=21a-21 equation:

Simplifying
9a + 123 = 21a + -21

Reorder the terms:
123 + 9a = 21a + -21

Reorder the terms:
123 + 9a = -21 + 21a

Solving
123 + 9a = -21 + 21a

Solving for variable 'a'.

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

Add '-21a' to each side of the equation.
123 + 9a + -21a = -21 + 21a + -21a

Combine like terms: 9a + -21a = -12a
123 + -12a = -21 + 21a + -21a

Combine like terms: 21a + -21a = 0
123 + -12a = -21 + 0
123 + -12a = -21

Add '-123' to each side of the equation.
123 + -123 + -12a = -21 + -123

Combine like terms: 123 + -123 = 0
0 + -12a = -21 + -123
-12a = -21 + -123

Combine like terms: -21 + -123 = -144
-12a = -144

Divide each side by '-12'.
a = 12

Simplifying
a = 12