SOLUTION
Write out the given parameters
Paperback Books $5
Hardcover Books $9
Magazines $2
Hence
1) The cost of 4 hardcover books is $36
To show the result on a number line we have the diagram below
2). 3 hardcover will costs
3 paperback books will cost
If Chico bought 3 hardcover rather than 3 paperback books
chico will spend
Hence, Chico will spend $12 more