Answer:
Part A: A. 7.50 x b
Part B: $90
Step-by-step explanation:
Part A: The cost of a book is $7.50, so the equation that is going to tell you the total cost of however many books purchased is equation A.
Part B: $90. If the cost of a book is $7.50 and the teacher purchases 12 books, you do $7.50 x 12= $90. You can check the equation by adding $7.50 12 times. You will get the same result.