From the question;
We are to convert the sentence
The cost of eight books and a $3 shipping fee
into an expression and simpilfy
Let the cost of a book = $x
then
The cost of eight books = $x times 8
= $8x
Since there is a shipping fee of $3
This means that
The Total Cost of the eight books will be
Total Cost of eight books = Cost of eight books + shipping fees
This gives
Total Cost of eight books = $8x + $3
Let
Total cost of eight books = Y
then this gives the equation below
Y = $8x + $3