Start by drawing your person in the balloon on your paper. Keep in mind for the next step that the person is looking down at a ship so somewhere in the distance, draw a ship and draw a line (a line sloping kind of like y=-x since the ship is lower than the balloon) connecting them. The angle between these two lines is said to be 21 degrees. Next drop a vertical line from the balloon to the ground level even with the ship. This height was said to be 2,000 ft. Lastly, draw a line connecting the ship and the point on ground level directly below the balloon and label it x. We know that the ground and line leading up to the balloon form a 90 degree angle, this we can use some trigonometry. Since we want to determine the horizontal distance x, we notice we have a given adjacent side and x is opposite to the angle. thus we can use tangent which relates opposite and adjacent sides.
Therefore, tan(21)=x/2000
Multiplying both sides by 2000, we get 2000tan(21)=x
Therefore, x=767.728 ft
Depending how you want to round, you may truncate as necessary
Hope this helps!
