a) $\frac{3}{5}$ + $\frac{-1}{7}$
= $\frac{21}{35}$ + $\frac{-5}{35}$
= $\frac{16}{35}$
b) $\frac{7}{36}$ - $\frac{5}{24}$
= $\frac{7}{36}$ - $\frac{5}{24}$
= $\frac{14}{72}$ - $\frac{15}{72}$
= $\frac{-1}{72}$
c) $\frac{3}{8}$ - $\frac{1}{5}$ + $\frac{3}{40}$
= $\frac{15}{40}$ - $\frac{8}{40}$ + $\frac{3}{40}$
= $\frac{7}{40}$ + $\frac{3}{40}$
= $\frac{10}{40}$
d) $\frac{5}{12}$ + $\frac{-11}{15}$ - $\frac{49}{60}$
= $\frac{25}{60}$ + $\frac{-44}{60}$ - $\frac{49}{60}$
= $\frac{-19}{60}$ - $\frac{49}{60}$
= $\frac{-68}{60}$ = $1$$\frac{-8}{60}$