for a right triangle we can use trigonometric ratios, this exercise wants we use tangent
[tex]\tan (\alpha)=\frac{O}{A}[/tex]where alpha is the reference angle, O the opposite side to the angle and A the adjacent side of the angle
Then using angle 30° like reference angle we replace
[tex]\tan (30)=\frac{5}{b}[/tex]because the opposite side from the 30°angle is 5cm and the adjacent side is b
Then right option is First
