if it is a right triangle, then it will satisfy the pythagorean theorem : a^2 + b^2 = c^2...where a and b are the legs and c is the hypotenuse.....and this theorem only works on right triangles
so lets sub and find out...
10^2 + 24^2 = 26^2
100 + 576 = 676
676 = 676 (correct)
so yes, this is a right triangle