An isosceles triangle is a triangle with two equal sides. Since, one of the angles is 90 degrees. Then, the 2 remaining must equal 90 because the total of the triangle should be 180 degrees. So, I think 45 degrees is the only one we can use here because 45 + 45 = 90 degrees.
I don't know a proper equation but here is how I solved it. 1/2 is 2/4 so I added a fourth of that 2/4 to the mile he ran before he twisted his ankle so 1/4 +3/4 = 4/4 or 1 mile. So then adding what's left of the 2/4, you have 1 1/4 = d.
