Suppose it takes X hours for A to play alone, and Y hours for B to play alone. Suppose the manuscript is 1 (which is the key of ontology), then the speed of A is 1/X, and the speed of B is 1/Y, that is to say, it is 4× 1/x = 6× 1/.

solve

X=0. 1

Y=0. 15

I am from Shanghai, too. I just graduated from college. These brothers and sisters are so poor that they are still repeating the old path we have taken. Quality education is just empty talk. How can such a difficult question come up?