If a square with a width of 30 feet a length of 72 feet, and the diagonal is 78 feet, would the square have right angles. Yes or No answer please explain

Yes. Use the Pythagorean theorem. 30 would be a. 72 would be B. 78 would be C.
Formula:
A^2 + B^2= C^2
A squared Plus B squared equals C squared

30 squared is 900
72 squared is 5184
900+5184 = 6084

78 squared is 6084

Therefore the triangle has a right angle.