Answer:
The first triangle
Explanation:
The Pythagoras theorem is used to calculate the side length of the right angle triangle.
The theorem says that the sum of the square of the two shorter legs of a right angle is equal to the square of the hypotenuse.
From the given triangles, the only one which is a right angle triangle is the one with side lengths 2 and 3 .
The first triangle from left to right.