Solution
= Solution
The condition $X>x_0$ selects positions $x_1$ and $x_2$. Their combined good-ball joint <probability> is $p(g_1+g_2)$, and their total <probability> is $p(g_1+g_2)+(1-p)(d_1+d_2)$. Thus
$$
\boxed{P(G\mid X>x_0)=\frac{p(g_1+g_2)}{p(g_1+g_2)+(1-p)(d_1+d_2)}
=\frac{p(1-g_0)}{p(1-g_0)+(1-p)(1-d_0)}.}
$$