Given the information on the problem, we can draw the following diagram:
notice that we have a right triangle,then, we can find the value of 'w' by using the trigonometric function tangent on the angle:
[tex]\begin{gathered} \tan (30)=\frac{\text{opposite side}}{adjacent\text{ side}}=\frac{120}{w} \\ \Rightarrow\tan (30)=\frac{120}{w} \\ \Rightarrow w\cdot\tan (30)=120 \\ \Rightarrow w=\frac{120}{\tan (30)}=207.8\approx208ft \\ w=208ft \end{gathered}[/tex]therefore, the river is 208 ft wide
