Please help. Somebody give an answer to this question please. I need a step by step explanation as well.

ANSWER:
15d^2+7d-4

STEP BY STEP:
you can use F.O.I.L. to solve this (first,outer,inner,last)

first you multiply both of the first values in each set of parentheses, 5d and 3d to get 15d^2, then you multiply the terms on the outside, 5d and -1 to get -5d. then multiply the inner values, 4 and 3d to get 12d. because 12d and -5d are like terms, you combine them to get 7d. lastly, you multiply the last values in each parentheses, 4 and -1 to get -4