设第一次运来的鱼为x.得:
x-37.5%x=4.2
(1-37.5%)x=4.2
62.5%x=4.2
x=4.2÷62.5%
x=6.72
6.72+4.2=10.92(吨)
答:两次一共运来10.92吨鱼.