Answer
$x=23$
Work Step by Step
$MN$ is the mid-segment of $\triangle ABC$. Therefore...
$MN= \frac{1}{2} BC$
Substitute in known values...
$(3x-11)= \frac{1}{2} (4x+24)$
Simplify the right side...
$3x-11=2x+12$
Subtract $2x$ from both sides...
$x-11=12$
Add eleven to both sides
$x=23$
