all right angles will follow the pythagorean theorem which is
[tex]a^2 +b^2 =c^2[/tex]
where c is always the longest side aka the hypothenuse
you can determine what side length KL is through the pythagorean theorem,
if it is equal to side length EF, then you can conclude that you have two congruent triangles through the SSS postulate (theorem?)
and thus meaning triangle EGF must also be a right triangle
