1) The distance between the two places is 390 kilometers. Motorcycles and cars start from these two places, face to face. If they leave at the same time, they will meet in 3.9 hours. If the motorcycle starts first, the car 1.2 hours later, and we will meet in 3 hours. Find the speed of two cars.

Speed sum: 390/3.9 =100 km/h.

* * * Equivalence:100 * 3 = 300km.

Motorcycle first: 390-300 = 90km.

Motorcycle speed: 90/ 1.2 = 75km.

There are two bags of rice. The weight of bag A is 125 kg, and that of bag B is 260 kg. How many kilograms are taken out of bag A and put into bag B, and the weight of bag B is twice that of bag A?

The result is that B is 260/ 125=2.08 times that of A. Can A still get it from B?

What you should take is:125-(125+260)/3 =-10/3, that is, from B to A, take10/3 kg, in which case B is twice as much as A.