% LMex020503_4th.m
% Example 2.5.3 Application of solve  p 63-64 in
% Larsen & Marx (2006) Introduction to Mathematical Statistics, 4th edition
% Written by Eugene.Gallagher@umb.edu, revised 1/15/11
% http://alpha.es.umb.edu/faculty/edg/files/edgwebp.html
%        Table 2.5.1
%          White  Black
%  Male     50     30
%  Female   40     x
% P(Black ^ Female) =   P(Black)     *   P(Female)
%     x/(120+x)     = (x+30)/(120+x) * (40+x)/(120+x)
syms x
solve(x/(120+x)-(40+x)/(120+x)*(30+x)/(120+x))