True/False:-

Opposite angles of a trapezium are equal.

We know that a regular trapezium has their non parallel sides equal and the angles on either side of the bases are equal.
Considering the trapezium PQRS as shown below;

Here PQ$\parallel$SR, and PS acts as transversal; so we have,
$$\begin{gathered} \angle \mathrm{P}+\angle \mathrm{S} = 180° ...\left(\mathrm{i}\right) \\ \mathrm{and}; \angle \mathrm{P} = \angle \mathrm{Q} ...\left(\mathrm{ii}\right) \\ \mathrm{so} \mathrm{from} \left(\mathrm{i}\right) \mathrm{and} \left(\mathrm{ii}\right) \mathrm{we} \mathrm{get}; \\ \angle \mathrm{Q}+\angle \mathrm{S} = 180° \\ \mathrm{Similarly}; \angle \mathrm{P}+\angle \mathrm{R} = 180° \end{gathered}$$
This means the sum of the opposite angles of trapezium is 180 degree.
Therefore the statement "Opposite angles of a trapezium are equal" is false.