（1/3+1/5）×1.5
=1/3×1.5+1/5×1.5
=0.5+0.3
=0.8
5.375-（3 又3/8-2 又1/3）
=5又3/8-3又3/8+2又1/3
=2+2又1/3
=4又1/3
0.91÷4/5+1.25×1.09
=0.91×1.25+1.25×1.09
=（0.91+1.09）×1.25
=2×1.25
=2.5
2009×2007/2008
=（2008+1）×2007/2008
=2007+2007/2008
=2007又2007/2008
16÷2.5
（2.25-2 1/4）÷3 2/7