-h/4+5 is your answer
Hope this helps.
Answer:

Step-by-step explanation:

1. x midpoint: (-9+4)/(2) = -2
2. y midpoint: (3+7)/(2) = 5
3. The midpoint is (-2,5)
It is a similar triangle so the side length of the smaller triangle (x and x-2) are in the same ratio as the bigger triangle (2x+5 and 2x-1). As the ratio is the same, you can equate them and solve for x.