PLS HELP, I DONT UNDERSTAND

 156 meters from the base, directly below the top edge of the platform

The ant walks 220.6 yards.

Step-by-step explanation:  In a right triangle with 45° angles, the base and the height are the same lengths (or in this example, distances) The stairway forms the hypotenuse if this triangle. If there is no wind blowing or anything else interfering with the vertical path of the dropped keys, they should be where the imaginary 90° angle would be formed.

Part 2  Use sine or cosine of 45° (both .707) .Divide 156/.707 ≈ 220.6 yards  

Part 3   a²+b²=c² .  a and b are equal, so   2(156²) = 48726

√48726 ≈ 220.6

c. side angle side. u shares the same sides