a) (-4/7)+(-2/21)+(+11/12)+(-9/14)=
-⁶4/7-²2/21+11/12-³9/14=
(-24-4-27)/42+11/12=
²-55/42+711/12=(-110+77)/84=-33/84=
-11/42
b)(+1/48)+(-3/16)+(+5/24)=
1/48-³3/16+²5/24=(1-9+10)/48=
2/48=1/24
c)(+5/6)+(+7/12)+(-2/3)+(-1/4)=
²5/6+7/12-⁴2/3-³1/4=
(10+7-8-3)/12=6/12=1/2