You want to solve for x so add 18 from both sides of the equal sign. making it 3x=12. then divide both sides by 3 making x=4. x is 4.
Kelsey must spend less than or equal to $65.
The expression 5.50b+7.5 is correct
Kelsey able to purchase 10 books.
On the end Kelsey can spend $2.50 to purchase small present (calendar or book for notes)
Answer:

Step-by-step explanation:
Given equation:

Solving for unknown variable 
Adding 8 both sides by additive property of equality.


Squaring both sides to remove the square root.


Adding 5 both sides by additive property of equality.


Dividing both sides by 6 to isolate 

∴ 