In the adjoining figure, $ABCD$ is a quadrilateral. How many pairs of opposite sides are there? Name them.

In the adjoining figure, $ABCD$ is a quadrilateral.

How many pairs of adjacent angles are there? Name them.

In the adjoining figure, $ABCD$ is a quadrilateral. How many pairs of opposite angles are there? Name them.

In the adjoining figure, $ABCD$ is a quadrilateral. How many diagonals are there? Name them.

Prove that the sum of the angles of a quadrilateral is $360°$.

The three angles of a quadrilateral are $76°, 54° \mathrm{and} 108°$. Find the measure of the fourth angle.

The angles of a quadrilateral are in the ratio $3:5:7:9$. Find the measure of each of these angles.

A quadrilateral has three acute angles, each measuring $75°$. Find the measure of the fourth angle.

Three angles of a quadrilateral are equal and the measure of the fourth angle is $120°$. Find the measure of each of the equal angles.