To find out whether or not a triangle is a right triangle, you have to figure out whether or not it satisfies the Pythagorean Theorem.
The Pythagorean Theorem says that the sum of the squares of the side lengths, represented by variables a and b, must equal the square of the hypotenuse, represented by c.
a² + b² = c²
20² + 48² = 52²
400 + 2304 = 2704
2704 = 2704
When we plug in the side lengths and simplify the Theorem, it results in a true statement, so we can conclude that yes, the triangle is a right triangle.