check the picture below.
so it has a base of 18x18 and a height of that much.

I did this equation and it’s A
Step-by-step explanation:

To find an angle you need to use trig ratios (tan, sin, and cos).
In this case to find ∠R you would need to use sin or cos because both of the legs are not across or adjacent to it.
To find ∠R you would need to do the "opposite" formula which would be (for sin) 5/13 <span>≈ 0.38.. asin = 22.26</span>