Find length CD first, which is the hypotenuse of the triangle.
PD = opposite
Opposite & hypotenuse = SOH or sin
Sin(27) = 15/H
x h, then ÷ sin(27)
H = 15/sin(27)
H = 33.04....
Move to triangle CDR:
15 is length opposite the angle we're after.
So far, we've got the hypotenuse (which we just found to be 33.04....) & the opposite of our triangle
Hypotenuse & opposite = SOH
Sin(x) = 15/33.04... but, to find the angle we do inverse of sin
sin-1(15/33.04...) = x
x = 27
(33.04... means I used the full numbers displayed on my calculator)
Thus, RCD is 27 degrees
Hope this helps!