The way to get the length of RS is actually very simple. You see how there is a number 17 in the line? You take that and it should mean every area where a line should be is 17. So, R is 17, the 2nd line is 17, M is 17, the 4th line is 17, and S is 17. So you then multiply 17 times 5 and get 85.
-Mabel <3
(Sorry if this is incorrect! <3)
