P=s1t-s2t. Which equation sauce for tea

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?

Each cookie sells for $0.50 sam spent $90 on baking supplies and each cookie cost $0.25 to make how many cookies does sam need to sell before making a profit formula: sales> cost

Amachine part consists of a half sphere and a cylinder, as shown in the figure. the total volume of the part is π cubic inches.