What is vertex ?

If a vertex of a triangle is (1, 1) and the midpoints of two sides through this vertex are (-1, 2) and (3, 2), then the centroid of the triangle is

In DeltaXYZ the biggest angle is at which vertex?

The diagonal of a square is 8x- 15y =0 and one vertex of the square is (1, 2). The equations to the sides of the square passing through this vertex are