Point A(-5,-7) turns into point A' (3,-7). The old x coordinate is added onto 8 to get the new x coordinate. Note how in the second point x = 6 --> x+8 = 6+8 = 14.
For the third point, we have x = 10 and we add 8 onto this to get x+8 = 10+8 = 18
Answer: 18
side note: the y coordinate stays the same for each transformation. This means every point shifts to the right 8 units