Answer:
This is a Pythagorean triple.
Explanation:
In order to find this, use the Pythagorean Theorem to and see if it gives a true statement.
a^2 + b^2 = c^2
15^2 + 20^2 = 25^2
225 + 400 = 625
625 = 625
Since this is a true statement, we know that this is a Pythagorean Triple.