Is there a way to do these problems without resorting to plugging in?

[gcf101]

<p>

@smash20 in post #1

<a href=“ImageShack - Best place for all of your image hosting and image sharing needs”>ImageShack - Best place for all of your image hosting and image sharing needs;
In rectangle PQRS above, what is the sum of a+b in terms of x?
A. 90+x
B. 180-x
C. 180+x
D. 270-x
E. 360-x

</p>

<p>Parallel to ajwchin (post #2):
let a=b=80 (then a+b=160)
x=90-10-10=70
Answer A is the only working choice:
90+70=160.</p>