What should be added to the following to get $1$.

$\frac{11}{15}$

What should be added to the following to get $1$.

$\frac{8}{35}$

What should be added to the following to get $1$.

$\frac{81}{100}$

What should be added to the following to get $1$.

$\frac{199}{200}$

What should be added to the following to get $1$.

$\frac{998}{1000}$

Solve the following.

$\frac{1}{9}+\frac{1}{3}$

Solve the following.

$\frac{1}{8}+\frac{1}{24}$

Solve the following.

$\frac{1}{4}+\frac{1}{20}$

Solve the following.

$\frac{1}{6}+\frac{1}{12}$