Cancellation Laws/Proof 2

Theorem
Let $G$ be a group.

Let $a, b, c \in G$.

Then:
 * $b a = c a \implies b = c$
 * $a b = a c \implies b = c$

Proof
From its definition, a group is a monoid, all of whose elements have inverses and thus are invertible.

From Invertible Element of Monoid is Cancellable, it follows that all its elements are therefore cancellable.