8*7=56
60-56=4
4÷( 15-7)= 1/2
60- 15× 1/2=52.5
5× 1/2=5/2=2.5
52.5+2.5=55
55÷5= 1 1
Need 1 1 cow.
2、 10×20=200 15× 10= 150
200- 150=50 50÷(20- 10)=5
200- 5×20= 100
25-5=20
100÷20=5
If 25 ticket gates are opened at the same time, the queue disappears after 5 minutes.