Sam plans to walk his dog for a distance of 1 mile. he walks 3/8 of a mile and stops to get a bottle of water. then walks 1/8 of a mile more and stops to say hello to a friend. how far does sam still need to walk his dog?

Based on what i know about mean, this doesn't add up.

Simplify the expression. -2/5(10+15m-20n)

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. how many hours after the truck's departure will the two meet?