HINT

Construct an equilateral triangle with one vertex on each of three given parallel lines.

Try this:

1. Take TWO sheets of paper.

2. Construct three parallel lines on one of them.

3. Lay the second sheet of paper over the top of the first and trace the three parallel lines.

4. With the two sheets of paper lying on top of one another, rotate the top sheet 60 degrees.

5. The center of rotation will be one of the vertices . . .

6. Look for how to determine the other two vertices.

NOTE: This is one strategy. There may be alternative strategies to explore. GSP is not needed, but it might be a useful tool to explore the rotation.