Answer:
Red triangle on the diagram
Explanation:
The center of dilation is point D(-5,1). The scale factor is 1/2. This means that all distances need to be halved.
If triangle ABC has vertices A(-1,7), B(7,9) and C(3,1), then the image triangle has vertices at points E(-3,4), G(1,5) and F(-1,1).
Points E, G and F are midpoints of the segments DA, DB and DC (see attached diagram for details).