Given :

Let $\overrightarrow{OP}=2\hat i+3\hat j+4\hat k$

Let $\overrightarrow{OQ}=4\hat i+\hat j-2\hat k$

Mid-point of two points is given by $\large\frac{\overrightarrow{OP}+\overrightarrow{OQ}}{2}$

$\Rightarrow \large\frac{2\hat i+3\hat j+4\hat k+4\hat i+\hat j-2\hat k}{2}$

$\Rightarrow \large\frac{ 6\hat i+4\hat j-2\hat k}{2}$

$\Rightarrow 3\hat i+2\hat j-\hat k$