MARKING AS BRAINLIST HELP ASAP

What is the missing reason in step 5? linear pair postulategivendefinition of complementary anglescongruent complements theorem

What is x3+3x2−16x−48 divided by x−1?

Me with this assignment ! i only partially understand, so explain. also it's a work sample. at the championship bike race, steve and paula were fighting for first place. steve was 175 feet ahead of paula and had only 300 feet left to go. he was very tired and was going only 9 feet per second. paula was desperate to catch up and was going 15 feet per second. who won the bike race and by how far did she/he win?