Answer: He spends more time trading stickers by 15 minutes. Step-by-step: 1 hour is 60 minutes. So 2 hours is 120 minutes. 120 minutes plus his 20 minutes is 140 minutes. Subtract it from his homework time and he spends 15 more minutes trading stickers.
The best one is 3:2 cause it is the most used way to write a ratio. 3:2 also means 3 divided by 2 or 3 out of 2 so that's why you would use the other 2.
