Hi! I'm happy to help!
To solve this problem, we need to find out what part isn't already listed.
We know that The entire line (SQ) is 80, and the part of the line that isn't RS (QR) is 33.4. The rest of the line must be the difference between 80, and 33.4. To find the difference we use subtraction:
80-33.4
44.6
So, RS is 44.6
I hope this was helpful, keep learning! :D
