So first, a parallelogram is a shape with 4 sides, opposite sides parallel to each other. So given the image and the question, I believe we are finding a 4th vertex/point on the graph that will connect with the other two to form a parallelogram. (This problem would be a lot easier if there was a grid.)
But the answer is (-1, -5).
Look at the right two vertex to find the x. See how the one towards the left has an x value of 2 greater/2 units right than the one towards the right? Look back at the left side, the x value is -3, so the x value of the 4th vertex must be 2 greater, which is -1.
Now the y value, you look at the top two vertex. Notice how the left one has a y value of 2 greater/2 units up than the one towards the right? So add 2 to -7, given by the bottom vertex, which is -5. Now plot and draw it, it makes sense!