The walking distance that is saved by cutting across the lot is

Using the Pythagorean Theorem, we have x^2+(x+2)^2=51^2, and
x^2+ x^2+4x+4=2x^2+4x+4=51^2. After that, we subtract 51^2 from both sides to get 2x^2+4x-2597. Using the quadratic formula (x=(-b+-sqrt(b^2-4ac))/2a in ax^2+bx+c), we get around 35 for x. We did + instead of minus after b due to that it can't be negative! x+2=37, so you save 35+37-51=around 21 feet

Letter c i’d say