Question

△DNS∼△ARH .

Answer 1

The answer is 33 units. 

Answer 2

$\Delta DNS \sim \Delta ARH \Longrightarrow \dfrac{DN}{AR} = \dfrac{DS}{AH} \\ \\ \dfrac{72}{21.6} = \dfrac{110}{x} \\ \\ \\ x = \dfrac{21.6 \times 110}{72} \\ \\ \\ x = \dfrac{2376}{72} \\ \\ \boxed{x = 33 \ units}$