27.8x10.2-27.8÷0.2
=27.8x10.2-27.8x5
=27.8x(10.2-5)
=27.8x5.2
=144.56为什么要把除以2变成乘以5除以0.2就是除以1/5嘛，除以1/5也就是乘5噻