The exercise is the following:
Let $R$ be a ring with unity $1\neq 0$ and let $I,J$ be minimal left ideals of $R$ (A left ideal $I$ is said to be a minimal left ideal if $I\neq 0$ and for every left ideal $J$ such that $0\subset J\subset I$, either $J=0$ or $J=I$).
Prove that $IJ=0$ or $IJ\cong J$ as left $R$-modules.
I don't understand the second conclusion. As $I,J$ are left-ideals then $IJ$ (which consist in all the finite sums of elements of the form $ij$ with $i\in I, j\in J$) is a left ideal contained in $J$, so by hypothesis $IJ=0$ or $IJ=J$.
Am I missing something?