A triangle has sides of lengths of 24, 143 and 145 is it a right triangle?

If it is a right triangle, Pythagorean's Theorem will be true.

h^2=x^2+y^2, the hypotenuse squared is equal to the sum of its sides squared

145^2=143^2+24^2

21025=20449+576

21025=21025

So yes, this is a right triangle.