#### Answer

The given set of numbers is a Pythagorean Triple.

#### Work Step by Step

In order for a set of numbers to be a Pythagorean Triple, they must be natural numbers that create a true statement when plugged into the Pythagorean Theorem. Let us plug in the three numbers given and simplify to see if they create a true statement: $$a^2+b^2=c^2$$$$15^2+20^2=25^2$$$$225+400=625$$$$625=625$$Since this is true, the given set of numbers is a Pythagorean Triple.