Write an equation for Greg ordered some books online for $6 each. He paid a total of $3 for shipping. The total cost of the purchase was $75.00. How many books did he buy?

Answer: he bought 12 books.

Step-by-step explanation:

Let x represent the number of books that Greg bought.

Greg ordered some books online for $6 each. This means that x books would cost $6x

He paid a total of $3 for shipping. The total cost of the purchase was $75.00. This means that

6x + 3 = 75

Subtracting 3 from the left hand side and the right hand side of the equation, it becomes

6x + 3 - 3 = 75 - 3

6x = 72

Dividing the left hand side and the right hand side of the equation by 6, it becomes

6x/6 = 72/6

x = 12