Macks Parking Garage charges 400 for the first hour and 250

Mack\'s Parking Garage charges $4.00 for the first hour and $2.50 for each additonal hour. For how long has a car been parked when the charge exceeds $16.50?

Solution

4+2.50X>16.50
2.50X>>16.50-4
2.50X>12.50
X>12.50/2.50
X>5 HOURS.
1 HOUR @ %4.00 + 5 HOURS @ $2.50=16.50
PROOF:
LET THE HOURS @ 2.50 BE 5.1 HOURS.
4+2.50*5.1>16.50
4+12.75>16.50
16.75>16.50