this means that the 3x angles is equal to 45 degrees and the 4x angle is equal to 60 degrees and the 5x angle is equal to 75 degrees. 45 + 60 + 75 = 180 degrees so we're good there. the angles are in the ratio of 3 to 4 to 5 which is as originally assumed, so we're good all around and that's your answer.