Answer:
3n^2-5n-28
Explanation:
FOIL: first inside outside last
Add together the products of the first two parts (n*3n=3n^2), the outer two parts (n*7=7n), the inner two parts (-4*3n=-12n), and the last two parts (-4*7=-28). Simplify, and your answer is 3n^2-5n-28.