Convert the following hexadecimal numbers into their decimal equivalents:
(a) $7 \mathrm{~A}_{16}$
(b) $3 \mathrm{~F}_{16}$
(a) $7 \mathrm{~A}_{16}=7 \times 16^{1}+\mathrm{A} \times 16^{0}=7 \times 16+10 \times 1$ $=112+10=122$
Thus $\mathbf{7 A}_{16}=\mathbf{1 2 2}_{10}$
(b) $3 \mathrm{~F}_{16}=3 \times 16^{1}+\mathrm{F} \times 16^{0}=3 \times 16+15 \times 1$ $=48+15=63$
Thus $3 \mathrm{~F}_{16}=63_{10}$