When a triangle is enlarged by a factor 3 are the angles tripled in size?

No - if the lengths of the sides are all increased by a factor of 3, the angles remain unchanged. You just wind up with a "similar" triangle 3 times the size of the original.

A quick counterexample would be to consider what would happen if the angles DID change. The sum of the angles in the original triangle should be 180°. If the angles in the new, larger triangle tripled in size, the sum of the angles in the bigger triangle would be 540° - but the sum of the angles of a triangle should always remain 180°.