Let $G=\langle x,y\mid x^3=e, y^2=e\rangle$ and otherwise unrestricted.
Let $H=\langle xyxy\rangle$.
Is $H\triangleleft G$?
And in that case, what is $$G/H$$ isomorphic to?
If it is a normal subgroup, I'd suspect $G/H\cong D_3$, but is that really true?