1. **State the problem:** We have an isosceles trapezium with the shorter parallel side on top and the longer parallel side on the bottom. The bottom interior angles are each 60°. We need to find the measure of the top interior angles, labeled $x^\circ$. 2. **Recall properties of trapeziums:** In any trapezium, the sum of the interior angles on the same side is 180°. Since the trapezium is isosceles, the top angles are equal, and the bottom angles are equal. 3. **Use the angle sum property:** Each bottom angle is 60°, so the adjacent top angle satisfies $$x + 60 = 180$$ because they are consecutive interior angles between the parallel sides. 4. **Solve for $x$:** $$x = 180 - 60 = 120$$ 5. **Conclusion:** Each top interior angle $x$ measures 120°. **Final answer:** $x = 120^\circ$