PLEASE HELP ME WITH THIS

see below

Step-by-step explanation:

Part A:

18.50 = .50c +3  where c is the number of cups

Part B

Profit = income - expenses

21 = .75c +3 - .10c

21 = .65c+3

Part C

Daria in part B makes more per cup ( the slope) as she makes .65 per cup and Sydney only make .50 per cup.  They both get the same amount in tip, but Daria will get more money overall ( 21 dollars versus 18.50)