Can someone help me on solving Quadratic and Exponential Functions

Question

Jerry wants to purchase some items whose cost function is C = 3x + 5, where x is the number of items. If Jerry spends between $50 and $80, find the minimum and maximum number of items that he can purchase

Answer 1

C = cost

 

50 < C < 80              "between" means not equal to 50 or 80

50 < 3x + 5 < 80      subtract 5 from all expressions

45 < 3x < 75

15 < x < 25

 

Jerry buys at least 15 yet less than 25 items.