After 20 days, the water in the first reservoir and the second reservoir is used up, and the water in the third reservoir is still one third of the total volume, which is the capacity of the first reservoir. The crux of the problem is: how many days does it take for ten outlets to discharge the water from the previous fifteen outlets for ten days? Assuming that the amount of water put into each drain every day is V and the number of days required is A, then:15×10× V =10× V× A, that is, it takes fifteen days, so it takes a total of thirty-five days.

Suppose the amount of grass in the pasture is originally A, B can grow every day, and every sheep eats Y every day. This grassland can feed 65,438+00 cows and 65,438+00 sheep for x days. system of equations

a+20b=64y×20

a+ 15b=72y× 15

a+xb=50y×x

If the calculation is correct, b=40y, a=480y and X should be equal to 48.