The definitions of the labels are:
- acute - less than 90°
- right - exactly 90°
- obtuse - more than 90°
- straight - exactly 180°
Since RQU is the sum of RQS, SQT and TQU, it measures 19+71+18 degrees, i.e. 108 degrees, and thus it's obtuse
Similarly, SQU is the sum of SQT and TQU, so it measures 71+18 = 89 degrees, so it's acute.
Finally, RQT is the sum of RQS and SQT, so it measures 19+71=90 degrees, and it's a right angle.
