Answer:
A. 21
Explanation:
Use the trigonometric function for the tangent of an angle because the adjacent side of the right-angled triangle is provided in the question, whilst the opposite side is x.
tan = opposite / adjacent
tan 60° = x / 7 * sqrt(3)
Now make x the subject of the equation.
x = tan 60° * 7 * sqrt(3)
x = 21
When multiplying, take into consideration all the digits on your calculator display.
Hope this helped!