Answer
See explanation
Work Step by Step
By hypothesis, $A$ is $5 \times 3, C$ is $3 \times 5,$ and $A C=I 3 .$ let $\mathrm{x}$ satisfies $\mathrm{Ax}=\mathrm{b} .$ Then $\mathrm{CAx}=\mathrm{Cb} .$ because $\mathrm{CA}=\mathrm{I}, \mathrm{x}$ must
be Cb. This shows that Cb is the only solution of $\mathrm{Ax}=b$
