Show that congruent arcs of a circle subtend equal angles at the centre.

In a given figure, if $\mathrm{AB}\parallel \mathrm{CD}$, then measure of $\angle \mathrm{AED}$ is:

In the given figure, if $l\parallel m$, then values of $x$ and $y$ are

In a figure, if $\mathrm{OP}\parallel \mathrm{RS}$, $\angle \mathrm{QRS}=130°$ and $\angle \mathrm{OPQ}=110°$, then $\angle \mathrm{PQR}$ is equal to:

For what value of $x$ will lines $p$ and $q$ be parallel to each other?