（1）（1-5/8）÷25/28-3/10 (2) 5/6-(1/2-1/3)÷4/9
=3/8÷25/28-3/10 ＝5/6－1/6÷4/9
=3/8*28/25-3/10 ＝5/6－3/8
=21/50-3/10 ＝11/24
=21/50-15/50
=6/50
五分之四乘八分之七+八分之七除以五 （一减十五分之八乘四分之三）除以五分之三
（1）（1-5/8）÷25/28-3/10 (2) 5/6-(1/2-1/3)÷4/9
=3/8÷25/28-3/10 ＝5/6－1/6÷4/9
=3/8*28/25-3/10 ＝5/6－3/8
=21/50-3/10 ＝11/24
=21/50-15/50
=6/50