0.25×63.5—1╱4×27╱2脱式计算=0.25×（63.5-13.5）=0.25×50=12.5
0.25×63.5—1/4×(27/2)=0.25x(63.5+13.5)=0.25x77=0.25x80-0.25x3=20-0.75=19.25
