Some one me if this is correct im bad at rounding

Two customers went to a post office. first customer paid $12 for 14 and 5 envelopes the second paid 24.80 for 10 postcards and 15 envelopes. what is cost of each envelope?

The paint recipe also calls for 1/4 cup of food coloring. tyler says mrs.mcglashan will also need 6 cups of food coloring. do u agree or disagree? explain.

Sally deposited money into a savings account paying 4% simple interest per year.the first year,she earned $75 in interest.how much interest will she earn during the following year?