What’s the missing leg?

Can someone me out here and the tell me the greatest common factor

Acar started driving from city a to city b, distance between which is 620 miles, at a rate of 60 mph. two hours later a truck left city b and started moving towards city a at a rate of 40 mph. what distance from city a is the point where the truck and the car will meet?

In the sixth grade 13 out of 20 students have a dog if there are 152 sixth grade students how many of them have a dog