SOLUTION
Let us give a pictorial view of the question.
Where
[tex]\theta\text{ is the angle of elevation}[/tex][tex]\begin{gathered} \tan \theta=\frac{opposite}{adjacent} \\ \tan \theta=\frac{100}{90} \end{gathered}[/tex][tex]\begin{gathered} \tan \theta=1.1111 \\ \theta=\tan ^{-1}(1.1111) \\ \theta=48.013^o \\ \theta=48^o(to\text{ the nearest degree)} \end{gathered}[/tex]Therefore, the angle of elevation is 48 degrees.