a)
6/71+ 69/61 -18/17 =(6*61*17+69*71*17-18*71*61)/71*61*17=
=(6222+83283-77958)/73627=
=11547/73627
c) 51/35-13/35-12/35=(51-13-12)/35=26/35
f) 5/43+23/14-18/43=23/14-13/43=(23*43-13*14)/14*43=(989-182)/602= =807/602
i) 16/103-5/103+7/103
=(16-5+7)/103=18/103