3/4x[(7/15-1/5)/2/3]=（3/4)(3/2)(7-3)/15=(9/8)(4/15)=3/10
(58+27）x8+19/27=85x8+19/27=680+19/27
9.56-4.875-1/8+1.44=9.56+1.44-(4.875+0.125)=11-5=6第一个看不懂7/15-1/5通分得：7/15-3/15=4/15