`a)-17/13+2/(135)+11/31+4/(13)+20/31`
`=[(-17/13)+4/(13)]+(11/31+20/31)+2/(135)`
`=-13/13+31/31+2/(135)`
`=(-1)+1+2/(135)`
`=0+2/(135)`
`=2/(135)`
`b)5/8+3/(17)+4/(18)+20/-17+(-2)/9+21/56`
`=5/8+3/(17)+2/9+(-20/17)+(-2/9)+3/8`
`=(5/8+3/8)+[3/(17)+(-20/17)]+[2/9+(-2/9)]`
`=8/8+(-17/17)+0`
`=1+(-1)`
`=0`
`c)(-5/(12)+6/(11))+(7/(17)+5/(11)+5/(12))`
`=(-5/12)+6/(11)+7/(17)+5/(11)+5/(12)`
`=[(-5/12)+5/(12)]+(6/(11)+5/(11))+7/(17)`
`=0+11/11+7/(17)`
`=1+7/(17)`
`=17/17+7/(17)`
`=24/17`
`d)(9/(16)+8/(-27))+(1+7/(16)+(-19)/27)`
`=9/(16)+(-8/27)+1+7/(16)+(-19/27)`
`=(9/(16)+7/(16))+[(-8/27)+(-19/27)]+1`
`=16/16+(-27/27)+1`
`=1+(-1)+1`
`=1`
`e)(17/21+5/9)+(-17/21+2/3+4/9)`
`=17/21+5/9+(-17/21)+2/3+4/9`
`=[17/21+(-17/21)]+(5/9+4/9)+2/3`
`=0+9/9+2/3`
`=1+2/3`
`=3/3+2/3`
`=5/3`
`f)((13)/5+7/(16))+(-15/16+6/(15))`
`=(13)/5+7/(16)+(-15/16)+2/(5)`
`=((13)/5+2/5)+[7/16+(-15/16)]`
`=15/5+(-8/16)`
`=3+(-1/2)`
`=6/2+(-1/2)`
`=5/2`
`g)(6-2 4/5).3 1/8 -1 3/5 : 1/4`
`=(6-(14)/5) . (25)/8 - 8/5 . 4`
`=((30)/5-(14)/5) . (25)/8 -(32)/5`
`=(16)/5 . (25)/8 - (32)/5`
`=10-(32)/5`
`=(50)/5-(32)/5`
`=(18)/5`
`h)-5/9+8/(15)+(-2)/(11)+4/-9+7/(15)`
`=[(-5/9)+(-4/9)]+(8/(15)+7/(15))+(-2/11)`
`=(-9/9)+15/15+(-2)/(11)`
`=(-1)+1+(-2/11)`
`=0+(-2/11)`
`=-2/(11)`
`i)5/(13)+(-5)/(17)+(-20)/(41)+8/(13)+(-21)/(41)`
`=(5/(13)+8/(13))+[(-20/41)+(-21)/(41)]+(-5/17)`
`=13/13+(-41/41)+(-5/17)`
`=1+(-1)+(-5/17)`
`=0+(-5/(17))`
`=-5/(17)`
`j)1/5+(-2/9)+(-7/9)+4/5+16/17`
`=[(-2/9)+(-7/9)]+(1/5+4/5)+16/17`
`=(-9/9)+5/5+16/17`
`=(-1)+1+16/17`
`=0+16/17`
`=16/17`