Hello!
for question one, I know this much:
If the square of the length of the longest side of a triangle is equal to the sum of the squares of the other two sides, then the triangle is a right triangle.
so, if 50^2=2500, and 14+48=62, then this is not a right triangle
and as for the second one, I do belive that if you use the refence of a graph, and say Sarah lives at (0,0) and move 12 right then 10 down, meaning her friend lives at (10,-12) there is a very complicated equation that follows, which I will not show to keep things simple for you.
they live approximately 15.620499 miles apart.
I hope this helps, and have a nice day!