a)

$40\frac{1}{2}:18=\frac{81}{2}\cdot \frac{1}{18}=\frac{9}{2}\cdot \frac{1}{2}=\frac{9}{4}=2\frac{1}{4}$

$18\cdot 2\frac{1}{4}=40\frac{1}{2}$

 

b)

$15\frac{5}{7}:5=15\frac{5}{7}\cdot \frac{1}{5}=\frac{110}{7}\cdot \frac{1}{5}=\frac{22}{7}\cdot \frac{1}{1}=3\frac{1}{7}$

$3\frac{1}{7}\cdot 5=15\frac{5}{7}$

 

c)

$109\frac{3}{5}:8=109:8+\frac{3}{5}:8=13\frac{5}{8}+\frac{3}{32}=13\frac{25}{40}+\frac{3}{40}=13\frac{28}{40}=13\frac{7}{10}$  

$<br>$

$8\cdot 13\frac{7}{10}=109\frac{3}{5}$

 

d)

$72\frac{6}{10}:11=\frac{72}{11}+\frac{6}{10}:11=\frac{72}{11}+\frac{6}{110}=\frac{720}{110}+\frac{6}{110}=\frac{726}{110}=6\frac{66}{110}=6\frac{33}{55}=6\frac{3}{5}$

$6\frac{3}{5}\cdot 11=72\frac{6}{10}$