Let's say the distance between the destination is 10 miles. The train will reach the destination in 30 min for the first round and 20 min the second. Now, we can say, the train took 50 min to go 20 miles. Which is also 24mph. (5min=2miles)
Since it said the number of dimes is 6 more than twice the number of nickels There are 36 dimes, this statement in an equation is d=(2n + 6), so then it would be [2(36) + 6] which is 72 + 6 = 78
