Please help and explain

Question

Rajan bought 5 copies of a book to give as gifts. The book was on sale for $5 off the original price. The total that Rajan spent on 5 books was $2 more than he would have spent on 4 copies of the book at the original price. What was the original price of the book? Write an expression and put a variable

Answer 1

The total that Rajan spent on 5 books was $2 more than he would have spent on 4 copies of the book at the original price
5x - 2 = 4y

The book was on sale for $5 off the original price. 
x = y - 5
Substitute:
5(y - 5) -2 = 4y
5y - 25 - 2 = 4y
y = 27
x = 22