15.5-9又10分之1+0.15
=15.5-9.1+0.15
=6.4+0.15
=6.55
9又6分之1+4.25+6.5
=9又1/6+4又1/4+6又1/2
=9又2/12+4又3/12+6又6/12
=13又5/12+6又6/12
=19又11/12
2.5+7.05-6又20分之9
=2.5+7.05-6.45
=9.55-6.45
=3.1