False - should be 7 root 5
Explanation:
y = hypotenuse, longest side (so, it's the value of c)
Using the value of x (21) & y as (14) in the equation a^2 + b^2 = c^2
I get the value of 7 root 3 as shown above, to be 7 root 5 instead.
I know part of the question is cut off, but I'm sure that it's asking you to prove wrong or right if the triangle could be a right-angle triangle (with right measurements) & it's one because the last missing angle is 90 degrees.
(Root means square root)
Hope this helps!