Answer:
(-5, 3)
Explanation:
Let O(x, y) be the centroid of the triangle.
The median of a triangle is a line segment that joins the vertex of a triangle to the midpoint of the opposite side. There are three medians in a triangle; and the medians of a triangle intersect at a point called the centroid.
The centroid of a triangle is gotten from the average of the x coordinates and the y coordinates of all the three vertices.
For Triangle ABC has vertices A (3,-3) B (-7,9) C (-11,3) and centroid O(x, y). Hence:

The centroid is at (-5, 3)