2 1/4 0.5 2 1/5 应该没错吧
21/40.521/5
1.2÷3/5=2 7/12-1/3=1/4 1.75乘2/7=0.7 1.2乘3/5=0.72 4/5-3/5=1/5 7/8-1/8=3/4
