Doubt from Allen Hatcher AT about CW Complex

Doubt from Allen Hatcher AT about CW Complex

I am trying to learn Cellular Homology from Allen Hatcher, but stuck in
first Lemma (2.34) itself. While introducing Cellular Homology Hatcher in
his AT, Section 2.2 Lemma 2.34 says $X^n/X^{n-1}$ is a wedge sum of $n$ -
spheres, one for each $n$- cell of $X$. Where $X$ is a $CW$ Complex.
I am unable to prove this, couldn't even think a bit how to start or where
to start. Please guide me.