The midpoint of the line segment $ AB $ is :
$$ M = \left(\dfrac{ 1 }{ 2 },~7\right) $$To find midpoint between points $ A(x_1,y_1) $ and $ B(x_2,y_2) $, we use formula:
$$ M = \left( \frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2} \right) $$In this example we have:
$$ \begin{aligned} & A \left(4,~3\right) \implies x_1 = 4 ~~\text{and}~~ y_1 = 3 \\[1 em] & B \left(-3,~11\right) \implies x_2 = -3 ~~\text{and}~~ y_2 = 11 \end{aligned} $$After substituting into above formula, we get:
$$ \begin{aligned} M & \left( \frac{ 4 + \left( -3\right) }{2}, \frac{ 3 + 11 }{2} \right) \\[1 em] M & \left( \frac{ 1 }{2}, \frac{ 14 }{2} \right) \\[1 em] M & \left(\dfrac{ 1 }{ 2 },~7\right) \end{aligned} $$