This one should be easy, so easy in fact that it should be possible to get the answer by plain googling, if only I could figure out the right terms to google.
Let's say that you have ideals $I_1 \subset I_2$ of a ring $R$. Is it then true that $R/I_2$ is isomorphic to a subring of $R/I_1$?
If so, where can I find a proof?
If not, what counterexample is there to offer?
Thanks in advance!
The ring $R/I_2$ is a quotient of $R/I_1$, but is not a subring in general. Take for instance $R = \mathbb{Z}$, $I_1 = 0$ and $I_2 = 2\Bbb{Z}$. Then $\Bbb{Z}/2\Bbb{Z}$ is not isomorphic to any subring of $\Bbb{Z}$.