Spreadsheet: I can't use solve()

[Macund]

Thanks for read and sorry i'm not good speaking english.I trying to use solve() writing on cells and program but don't give me the answer. Example:
When i write =solve( B+34=0,B) give me {B}
When i write =rp(A1,A2,A3) give me {B}

EXPORT rp(A,C,D)
BEGIN
LOCAL E1;
200/(('B'-A)*(C*'B'-A))=D▶E1;
RETURN solve(E1,'B');
END;

What i can do ? When i change RETURN solve(E1,'B') to RETURN E1. Hp write the equation whith the numeric valors.For that i think i use wrong solve().