7分之2加5分之4 1减16分之9 15分之8减3分之1 11分之4加7分之6

2/7+4/5
=10/35+28/35
=38/35
=1+3/35
=1又3/35
1-9/16
=16/16-9/16
=7/16
8/15-1/3
=8/15-5/15
=3/15
=1/5
4/11+6/7
=28/77+66/77
=94/77
=1+17/77
=1又17/77