Let's denote the third side of the triangle as "X".
We know that the perimeter of a triangle is the sum of its three sides, so we can write an equation:
12.125 + 12.125 + × = 37.5
Simplifying the left side, we get
24.25 + × = 37.5
Subtracting 24.25 from both sides, we get:
× = 13.25
Therefore, the third side of the triangle measures 13.25 yards.