七又六分之五-六又十二分之七+五又二十分之九-四又三十分之十一+三又四十二分之十三-二又五十六分之十五+一又七十二分之十七
=7+1/2+1/3-6-1/3-1/4+5+1/4+1/5-4-1/5-1/6+3+1/6+1/7-2-1/7-1/8+1+1/8+1/9
=(7-6)+(5-4)+(3-2)+1+1/2+1/9
=4+1/2+1/9
=4又11/18
七又六分之五-六又十二分之七+五又二十分之九-四又三十分之十一+三又四十二分之十三-二又五十六分之十五+一又七十二分之十七
=7+1/2+1/3-6-1/3-1/4+5+1/4+1/5-4-1/5-1/6+3+1/6+1/7-2-1/7-1/8+1+1/8+1/9
=(7-6)+(5-4)+(3-2)+1+1/2+1/9
=4+1/2+1/9
=4又11/18