Ms.lemon has 150 to spend on the parking

You can make the equation 18+16.5x=150 with the info given

to solve this you first subtract 18 from both sides 

18+16.5x=150
-18            -18
16.5x=132

now divide both sides by 16.5 

16.5x=132
/16.5     /16.5
x=8 

therefor she can bring 8 people to the zoo (including herself)

Ends up on the 5th floor

Step-by-step explanation:

10-9+19-3-12

(10+19)-(12+3+9)

29-24

5