Answer
See below.
Work Step by Step
$S=\pi r(h+k)=\pi rh+\pi rk\\S-\pi rk=\pi rh\\h=\frac{S-\pi rk}{\pi r}$
Thus plugging in $S=50,k=3,r=2$: $h=\frac{50-\pi 2\cdot3}{\pi \cdot2}\approx 5.0$
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