Let $|G|=200$. Show that G is solvable.
My beginning of the proof:
- $|G|=200=2^3*5^2$
- Let $n_5$ be the number of Sylow p-subgroups. Then $n_5|8$ and $n_5\equiv1 mod5$. And it implies that $n_5=1$.
- From 2. we know that there exists $N$, such that $N\unlhd G$ and $|N|=25$.
What should be my next steps?
You're almost there:
$\;N\;$ is solvable (why?)
$\;G/N\;$ is also solvable (again, why?)
and thus $\;G\;$ is solvable.