Factor completely, word problem please help?

First, you need to subtract the cost of producing n shirts from the revenue gained from the sale of n shirts, so (n^3 + 2n^2) - (12n - 2n^2). If you carry through the minus sign, you'll get n^3 + 2n^2 -12n +2n^2. When you add like terms (combine the n squared sets) you get n^3 + 4n^2 - 12n. The n is a common factor, so you can factor it out: n(n^2 + 4n -12) Then you need two numbers that multiply to make -12 and add together to make +4. The numbers that multiply to give you -12 are: -3 and 4, -4 and 3, -6 and 2, -2 and 6. Only -2 and 6 adds up to +4. To factor the expression, you use the form (n plus the first term) times (n plus the second term). Since your terms are -2 and 6, the complete answer would be n(n-2)(n+6).