$a)\frac{3}{4}\cdot 60\min =\frac{180}{4}=45\min$

$\frac{2}{3}\cdot 60\min =\frac{120}{3}=40\min$ $\frac{2}{3}\cdot 60\min =\frac{120}{3}=40\min$

$2\frac{2}{5}\cdot 60\min =\frac{12}{5}\cdot 60\min =\frac{12}{5}\cdot \frac{60}{1}=\frac{12}{1}\cdot \frac{12}{1}=144\min$

$\frac{1}{6}\cdot 60\min =\frac{60}{6}=10\min$

 

$b)\frac{1}{8}\cdot 24=\frac{24}{8}=3$

$\frac{5}{12}\cdot 24=\frac{5}{1}\cdot 2=10$

$\frac{3}{4}\cdot 24=\frac{3}{1}\cdot 6=18$

$\frac{1}{3}\cdot 24=\frac{24}{3}=8$