3a+6=5a+21

Solution for 3a+6=5a+21 equation:

Simplifying
3a + 6 = 5a + 21

Reorder the terms:
6 + 3a = 5a + 21

Reorder the terms:
6 + 3a = 21 + 5a

Solving
6 + 3a = 21 + 5a

Solving for variable 'a'.

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

Add '-5a' to each side of the equation.
6 + 3a + -5a = 21 + 5a + -5a

Combine like terms: 3a + -5a = -2a
6 + -2a = 21 + 5a + -5a

Combine like terms: 5a + -5a = 0
6 + -2a = 21 + 0
6 + -2a = 21

Add '-6' to each side of the equation.
6 + -6 + -2a = 21 + -6

Combine like terms: 6 + -6 = 0
0 + -2a = 21 + -6
-2a = 21 + -6

Combine like terms: 21 + -6 = 15
-2a = 15

Divide each side by '-2'.
a = -7.5

Simplifying
a = -7.5