SOLUTION
Write out the given parameters
Paperback Books $5
Hardcover Books $9
Magazines $2
[tex]\begin{gathered} \text{ The cost of 1 Hardcover books =\$9} \\ 4\text{ hardcover books will be } \\ 4\times9\text{ = \$36} \end{gathered}[/tex]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
[tex]3\times9=27[/tex]3 paperback books will cost
[tex]5\text{ }\times3=15[/tex]If Chico bought 3 hardcover rather than 3 paperback books
chico will spend
[tex]27-15=12[/tex]Hence, Chico will spend $12 more