$3 * \frac{5}{16} = \frac{3 * 5}{16} = \frac{15}{16}$

$\frac{7}{24} * 8 = \frac{7 * 8}{24} = \frac{7 * 1}{3} = \frac{7}{3} = 2\frac{1}{3}$

$\frac{13}{15} * 30 = \frac{13 * 30}{15} = \frac{13 * 2}{1} = 26$

$18 * \frac{7}{12} = \frac{18 * 7}{12} = \frac{3 * 7}{2} = \frac{21}{2} = 10\frac{1}{2}$