Solve equation a+6a-9=30

To solve any equation, we have to get the variables and the constants (numbers) on opposite sides of the equals sign.  

First, we have to combine the like terms on the left side of the equation, resulting in

7a - 9 = 30

Then, because we want the constants on the right side of the equation, we have to +9 to cancel out the -9 on the left side.

7a=39

Next, the a has a coefficient of 7, which it is multiplied by.  To undo multiplication, you have to divide.  Therefore, we should divide both sides by 7.

a= 5 4/7 or 5.57142857143

In improper fraction form, a = 39/7, as this fraction cannot be simplified any farther.

Where is it shown below?