Someone please please help me this is a test and I have no clue what the answer is for 4 and 5

Molly shared a spool of ribbon with 12 people. each person received 3 feet of ribbon. which equation can she use to find r, the number of feet of ribbon that her spool originally had?

I’m still confused on how to work the percentages

The function p(x) = –2(x – 9)2 + 100 is used to determine the profit on t-shirts sold for x dollars. what would the profit from sales be if the price of the t-shirts were $15 apiece?