Respuesta :

Answer:

5

Step-by-step explanation:

1. the formula of the midpoint is:

[tex]X_M=\frac{X_C+X_D}{2}; \ Y_M=\frac{Y_C+Y_D}{2}.[/tex]

2. using the formula of coordinate 'y':

[tex]7=\frac{x+9}{2}; \ x=5.[/tex]