Answer
$7.5$
Work Step by Step
To find the midpoint between points $(x_1,y_1)$ and $(x_2,y_2)$, we use the midpoint formula:
$\displaystyle Midpoint=(\frac{x_1+x_2}{2},\frac{y_1+y_2}{2})$
We know that the midpoint between points $(4,6)$ and $(5,9)$ would be:
midpoint=$(\displaystyle \frac{4+5}{2},\frac{6+9}{2})$
$=(\frac{9}{2},\frac{15}{2})$
$=(4.5,7.5)$
Thus the $y$ value that corresponds to an $x$ value of $4.5$ is $7.5$.