Why is the norm of a matrix-vector product less than or equal to the product of the matrix and vector norms?

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In a textbook, I came across matrix norms induced from vector norms, and it says:

$$ ||A x|| \le ||A||\cdot||x|| $$ $A \in \mathbb{R}^{NxN},\ x \in \mathbb{R}^N$.

May I please ask for a gentle proof on why is this the case?