You can subtract 5.5 from 16 to calculate the amount of money exceeding 1 hour as 10.5 yuan, and then divide 10.5 by 7 to calculate 1.5 hours, that is, more than 1.5 hours, initially.
Money spent exceeding 1 hour: 16-5.5= 10.5 (yuan)
Charge per hour for exceeding 1 hour: 3.5÷0.5=7 (Yuan)
Time exceeding 1 hour:10.5÷ 7 =10.5 (hour)
* * * Parking time: 1+ 1.5=2.5 (hours)
So you can answer: Dad stopped for 2.5 hours.