The sum of all three angle measures in a triangle will always equal 180 degrees. So, if you subtract 63 and 27 from 180 you will have your third angle measure, which is 90.
So now your 3 measures are 63, 27, and 90. Since one of the angles is a 90-degree angle, the triangle must be a right angle because a right angle has a measure of 90 degrees.
EXPLANATION We are looking for the number of adult tickets sold. number of adult tickets sold =x We are given that there were 61 more student tickets sold than adult tickets. number of student tickets sold =+x61 The total number of tickets sold was 511.