6.72-3.28-1.72
=6.72-(3.28+1.72)
=6.72-5
=1.72我还有一道题可以教教我么可以12分之5除以7+12分之7乘以7分之1=简算12分之5除以7+12分之7乘以7分之1=5/12÷7+7/12÷7=（5/12+7/12)÷7=1÷7=1/7