6a-9=12+3a

Subtract 3a from both sides of the equation.

6a-9-3a=12

Subtract 3a from 6a.

3a-9=12

3a-9=12

Add 9 to both sides of the equation.

3a=12+9

Add 12 and 9.

3a=21

3a=21

Divide each term in 3a=21 by 3.

3a3=213

Cancel the common factor of 3.

Cancel the common factor.

3a3=213

Divide a by 1.

a=213

a=213

Divide 21 by 3.

a=7

a=7

Solve for a 6a-9=12+3a