Since the angle of depression is 10 degrees, the interior angle adjacent to the angle of depression is 90-10, or 80 degrees
Since the cosine the adjacent angle divided by the hypotenuse, we can use the cosine to help us solve this question. Divide 500 by the cosine of 80 degrees.
[tex]\dfrac{500}{\cos(80)} \approx 2897.4[/tex]
This may seem large, but this should be the answer for x. I hope this helps! ;)