Find the sum:

$\frac{-7}{8}+\frac{-4}{3}$

Find the sum:

$\frac{-14}{15}+\frac{7}{5}$

Find the sum:

$\frac{4}{9}+\frac{-7}{11}$

Subtract:

$\frac{-3}{4}$from $\frac{1}{2}$

Subtract: $\frac{-7}{18}$ from $\frac{-2}{9}$.

If the required answer is of the form $\frac{a}{b}$, then what is the value of $b$ in the simplest form? 

Subtract:

$\frac{4}{17} \mathrm{from} \frac{-8}{34}$

Subtract:

$\frac{-4}{11} \mathrm{from} \frac{-6}{7}$