Past exam of the mathematics course of the University of Cambridge / 2007 / ia / Paper 3 / 6D / iv / Solution

Can be false. Use $G=S_3$ and the normal subgroup $H=A_3$ from the root solution. The subgroup $H$ is cyclic of order three, hence an abelian group, and the quotient group has the two cosets $A_3$ and $(12)A_3$, so is cyclic of order two and abelian. Yet $(12)(23)=(123)$ whereas $(23)(12)=(132)$, proving that $S_3$ is not abelian. An abelian kernel and an abelian quotient do not force all elements of the original group to commute.