4.28x1/7+6.72x25/100-1/4=4.28x1/4+6.72x1/4-1/4=(4.28+6.72-1)x1/4=(11-1)x1/4=10x1/4=5/2(2又2分之1)
=1.07+1.68-0.25=1.02+0.5+1.68-0.25=2.7-0.25=2.45
