Question 935749
Some information is missing, but an assumption is possible from your description.  If Gary is looking and can see the far part of the bottom of the well  (and assumed empty), then there are formed TWO right triangles, SIMILAR.  The large right triangle has base {{{6+2=8}}} feet and the height of the triangle is {{{6+y}}}, using y as the depth of the empty well from top to bottom.


The smaller triangle is formed from Gary (6 feet) and the distance from his feet to the nearest part of the top of the well  (2 feet).


The sides of the similar triangles are in proportion.
{{{(6+y)/8=6/2}}}, and solving for y is easy and simple.


The choices you are asked to use are inconistant with the analysis just given, so information was missing from your problem description, which would expected to have been shown in a picture or diagram/figure.