A store sells pencils for $0.50 each and erasers for $0.75 each. If a student buys a total of 10 items for $6.00, how many pencils did the student buy?
In a practical problem, if a car travels 60 km/h and a truck travels 40 km/h, how long will it take for the car to catch up with the truck if the truck had a 30-minute head start?