1) Since this is a right triangle, we can apply the tangent of 60º and then find the opposite leg to angle as our first step.
[tex]\begin{gathered} \tan(60)=\frac{BC}{21} \\ BC=21\times\tan(60) \\ BC=21\times\sqrt{3} \\ BC=21\sqrt{3}\approx36.3703 \end{gathered}[/tex]2) We can use the Pythagorean Relation to find the hypotenuse:
[tex]\begin{gathered} CA^2=21^2+(21\sqrt{3})^2 \\ CA=\sqrt{21^2+(21\sqrt{3})^2} \\ CA=42 \end{gathered}[/tex]Thus, this is the answer:
21, 36.37, 42
Considering that 21 times the square root of 3 is approximately 36.3700 and the fact that the other choices are wrong, I believe the right one is B. Even though you should talk to your Teacher. Maybe there was a rounding mistake from the question itself.