The answer is n(9m-17p-2)
So you would first multiply the whole equations by 1/3, that would look like
1*n(-6+27m-51p)/3 that would equal n(-6+27m-51p)/3
In order for you to get it out of fraction mode you have to multiply the numerator and denominator by 3 and then your answer would be n(9m-17p-2).