The equation is .

Apply zero product property: If ab = 0 then a = 0, b = 0.

First .

Apply subtraction property of equality: If a = b then a b = b a.

Subtract 4 from each side.

Apply additive inverse property: .

Second .

Apply subtraction property of equality: If a = b then a + b = b + a.

Add 15 to each side.

Apply additive inverse property: 1515 = 0.

Divide each side by 3.

Check:

To check the solution substitute in .

Apply additive inverse property: .

The first solution is true.

To check the solution substitute in .

Apply additive inverse property: 15 + 15 = 0.

The first solution is true.

The values of q = 4, 5.