x/60+x(60-5)/(x+5)+[15-5x/60-5x(60-5)/(x+5)/]60=x/60+(15-x)/5
x(60-5)/(x+5)+[15-5x/60-5x(60-5)/(x+5)/]60=(15-x)/5
55x/(x+5)+[15-5x/60-5*55/(x+5)/60]=(15-x)/5
55x/(x+5)+[15-5x-275/(x+5)/360]=(15-x)/5
15-x=5* 55x/(x+5)+[15-5x-275/(x+5)/360]
15-x=275/(x+5)+[15-5x-275/(x+5)/360]
x=15-275/(x+5)+[15-5x-275/(x+5)/360]
x=275/(x+5)+[5x-275/(x+5)/360]
x=275/(x+5)+[5x-55/（x+5）]
——
72
x=（275+55)/(x+5)/3+5x
——
72