A train from Wuhan to Hefei, the original speed is 120 km / h, to 4 hours to arrive. After the train extraction, the speed reached 160 km / h, now from Wuhan to Hefei by train need a few hours?

A train from Wuhan to Hefei, the original speed is 120 km / h, to 4 hours to arrive. After the train extraction, the speed reached 160 km / h, now from Wuhan to Hefei by train need a few hours?

120x4 = 480 (total distance)
480/160=3
So it takes three hours

f(x)={2x+1,x

Isn't that obvious? The first question is X

Today, there is a town that does not know its size. Each town opens its door in the middle. Twenty steps out of the north gate, there are trees. Fourteen steps out of the south gate, and one thousand and seventy-five steps westward, there are trees. How about the town?