So seeing as you are given the values for P, R and t, the first thing you need to do is substitute the letters for their given numbers into the equation: Q = (36) / ((3)(4 - (-2)) Now expand out the brackets. Remember that a negative multiplied by a negative equals a positive. Picture an imaginary 1 before the -2. So, -1(-2) = -1-2 = 2, Q = 36 / (3 * 2), Q = 36 / 6, Q = 6