Hello there. To solve this question, we'll have to remember some properties about rotations.
Given the red and black triangles in the graph, we have to name the rotation that maps the black triangle onto the red triangle.
Even though they are displaced (that is, the black triangle will not be at the exact same place as the red after the rotation), we still can name this rotation.
We start by taking a point of which we can start the rotation of the triangle, as the axis of rotation. Notice the point at the vertex (1, -3), which we'll be referring as A from now on.
In this case, if we apply a 180º rotation on the triangle with respect to the axis at the vertex A.
Imagine a axis leaving the plane, such that a rotation like this would give us:
That is exactly what the triangle red is.
The rotation is in fact a 180º rotation (can be either clockwise or anticlockwise)
We can also use complex numbers to find that this might be a 180º rotation.