25pi/3=1/2xsquare root of 100x^2 and plus 50 arcsin(x/10)
If I correctly parse your sloppy notation, I get
25π/3 = 1/2 x√(100x^2) + 50 arcsin(x/10)
I doubt that is correct, but it is satisfied by x ≈ 1.84
Maybe you can clarify the problem a bit, using real math symbols and proper parentheses...