Hello there,
Okay, Let's start with RS. So what I did was I subtracted (3x-4)-(4x+1) and the reason I did that was because (4x+1) equal's the whole length. And sense I dont know the length of RS yet. . . I will use the other length to find out. So when you calculate those both. Your correct answer is (x+5).
RS= x=5
Hope this helps.
~Jurgen