a. $\frac{1}{12}$ + $\frac{-1}{6}$ = $\frac{1}{12}$ + $\frac{-2}{12}$ = $\frac{-1}{12}$
b. $\frac{-7}{16}$ - $\frac{1}{18}$ = $\frac{-63}{144}$ - $\frac{8}{144}$ = $\frac{-55}{144}$
c. $\frac{7}{21}$ - $\frac{-5}{27}$ = $\frac{1}{3}$ - $\frac{-5}{27}$ = $\frac{9}{27}$ + $\frac{5}{27}$ = $\frac{14}{27}$
d. $\frac{-5}{12}$ - $\frac{4}{9}$ + $\frac{11}{6}$ = $\frac{-15}{36}$ - $\frac{16}{36}$ + $\frac{66}{36}$ = $\frac{35}{36}$
e. $\frac{-5}{12}$ + $\frac{4}{9}$ - $\frac{11}{6}$ = $\frac{-15}{36}$ + $\frac{16}{36}$ - $\frac{66}{36}$ = $\frac{-65}{36}$