Use b(x)=x2\displaystyle {b}{\left({x}\right)}={x}^{{2}} and j(x)=x3\displaystyle {j}{\left({x}\right)}={x}-{3} to solve:

 (bj)(x)=(jb)(x)\displaystyle {\left({b}\circ{j}\right)}{\left({x}\right)}={\left({j}\circ{b}\right)}{\left({x}\right)} 

 x=\displaystyle {x}=