X+ 10 = Y-20 = 2 * Z = N/2 X = Y-30 Z =(Y-20)/2n =(Y-20)* 2

X+Y+Z+N=370

Y-30+Y+(Y-20)/2+(Y-20)*2=370

Y= 100 A: B actually did 100.

Second, the solution: the original price of a pen is X yuan.

2 16/X+3 = 2 16/(X- 1)

X=9

The original price of this pen is 9 yuan.

Third, the solution: A needs 240/4*2= 120 seconds to run a round trip, B needs 240/5*2=96 seconds, and C needs 240/3*2= 160 seconds.

C runs the slowest, so when three people start from the starting point again at the same time, the distance between A and B should be C.

Integer multiple of.

After 480 seconds, A ran four laps back to the starting point, B ran five laps and C ran three laps.

Starting point.

Solution: After X hours, Party A and Party B will meet.

There are 6X+4X= 100 X= 10.

The distance traveled by dogs is10 *10 =100 km.

A: The dog walked 100 km.