Explanation

(b)
$\log_{4}{(x - 1) = \log_{2}{(x - 3)}}$
$\Rightarrow \log_{4}{(x - 1) = 2\log_{4}{(x - 3) = \log_{4}(x - 3)^{2}}}$
$\Rightarrow x - 1 = x^{2} + 9 - 6x$
$\Rightarrow x^{2} - 7x + 10 = 0$
$\Rightarrow x = 5$ or 2
Hence, $x = 5$ $\lbrack\because x = 2$ makes $log(x - 3)$ undefined]
$\therefore$ Number of solution is 1