a) \(\dfrac{1}{2}\times\dfrac{1}{3}\times\dfrac{1}{4}=\dfrac{1}{6}\times\dfrac{1}{4}=\dfrac{1}{24}\)
b) \(\dfrac{1}{2}\div\dfrac{1}{3}\div\dfrac{1}{4}=\dfrac{1}{2}\times\dfrac{3}{1}\div\dfrac{1}{4}=\dfrac{3}{2}\div\dfrac{1}{4}=\dfrac{3}{2}\times\dfrac{4}{1}=\dfrac{12}{2}=6\)
c) \(\dfrac{1}{3}\times\dfrac{1}{5}\div\dfrac{1}{7}=\dfrac{1}{15}\div\dfrac{1}{7}=\dfrac{1}{15}\times\dfrac{7}{1}=\dfrac{7}{15}\)