Answer:
Each book costs [tex]13[/tex] dollars.
Step-by-step explanation:
Let [tex]b[/tex] be the cost, in dollars, of each book.
If you buy [tex]7[/tex] books, the total cost of books bought is [tex]7\times b[/tex]. If you had [tex]105[/tex] dollars and used some of it to buy books, then your remaining money would be expressed as [tex]105 -7b[/tex]. It also told as that after Mike bought those [tex]7[/tex] books, he had [tex]14[/tex] dollars left. So, [tex]105 -7 \times b = 14[/tex].
Solving for [tex]b[/tex]:
[tex]105 -7 \times b = 14 \\ 105 - 7 \times b -105 = 14 - 105 \\ - 7 \times b = -91 \\ \frac{-7 \times b}{-7} = \frac{-91}{-7} \\ b = 13[/tex]
