Answer:
Each book costed $34.
Step-by-step explanation:
Let the cost of a book be x.
[tex]324-9x=18[/tex]
Add 9x to both sides:
[tex]324=18+9x[/tex]
Subtract 18 from both sides:
[tex]306=9x[/tex]
[tex]9x=306[/tex]
Divide both sides by 9:
[tex]x=34[/tex]
Each book costed $34.