1, the truck from a city to b city, with a speed of 60 kilometers per hour, 12 hours to reach b city. Return to Jiacheng along the original road at a speed of 40 kilometers per hour. Find the average speed of this truck going back and forth.

(60× 12÷40)= 18 hours

720÷( 12+ 18)=48

The average speed of this truck is 48 kilometers per hour.

2, build a road, 25% of the total length was built on the first day, 20 kilometers were built the next day, and two-thirds of the total length was not repaired. How many kilometers is this road?

20÷( 1- 1/4-2/3)= 20÷ 1/ 12 = 240km。

This road is 240 kilometers long.

It costs 30 yuan to buy a pencil box and five pencils. The price of a pencil box is 25 times that of each pencil. How much is each pencil box?

Each pencil box is set at X yuan.

x+5*x÷25=30

x+x/5=30

5x+x= 150

6x= 150

x=25

Every pencil box, 25 yuan.