Factor the common factor out of –12 + 15x

Tina practice piano for 15 hours last month and 45 hours this month use multiplication to write a statement comparing me i was tina practice during the two months use addition to write a statement comparing the hours tina practice during the two months

Enter the number of complex zeros for the polynomial function f(x) = x 4+ 5x² +6

Pls! does anybody know a shortcut for answering these types of questions in the future?