sin(19.8º) ≈ 0.339 so the question should have been either what is asin(0.339) or what is sin(19.8º).
The range of sine is -1 to +1 so there is no angle whose sine is 19.8.
You need to supply distances between A and B and B and C in km for this to make sense.
You want
(x + c)2 = k
Expand the left-hand side
x2 + 2cx + c2 = k
Compare each term with
x2 + 3x = -3
Clearly we need 2c = 3, so c = 3/2. That means we must add c2 = 9/4 to each side (so k = -3 + 9/4 = -3/4)
(x + 3/2)2 = -3/4
As follows:
Like so:
Triangles BCF and EDF are similar so y/20 = 9/10
You can take it from here.
Brute force testing shows there are none!
(3a - 5)(b - 4) = 3ab - 12a - 5b + 20
+33652 
