Answer
Their center of mass moves $1.54m$ in the direction of the $-x$ axis.
Work Step by Step
1) At the original positions:
We have $m_J=86kg$, $m_B=55kg$, $x_J=+9m$, $x_B=+2m$ $$x_{cm, 0}=\frac{m_Jx_J+m_Bx_B}{m_J+m_B}=+6.27m$$
2) After switching:
We have $m_J=86kg$, $m_B=55kg$, $x_J=+2m$, $x_B=+9m$ $$x_{cm, f}=\frac{m_Jx_J+m_Bx_B}{m_J+m_B}=+4.73m$$
Their center of mass moves $6.27-4.73=1.54m$ in the direction of the $-x$ axis.
