What is the relationship between all triangles that can be drawn given the same three angles

Which best explains why this triangle is or is not a right triangle?

Pamela has a 30-year, 5.75% mortgage on her $250,000 home. she has been paying on it for 5 years, and has recently hit some financial trouble. if her lender agreed to lower the interest rate on her $231,905.47 balance to 5.5%, what will her new payment be for the remainder of the loan?

Algebraically prove that a clockwise and counterclockwise rotation of 180° about the origin for triangle abc are equivalent rotations.