Multiplying fractions is just multiplying the numerators together and the denominators together.
[tex]\sf\dfrac{4}{7}\times\dfrac{1}{4}\rightarrow\dfrac{4\times 1}{7\times 4}\rightarrow\dfrac{4}{28}\rightarrow\dfrac{1}{7}[/tex]
[tex]\sf\dfrac{4}{7}\times\dfrac{1}{6}\rightarrow\dfrac{4\times 1}{7\times 6}\rightarrow\dfrac{4}{42}\rightarrow\dfrac{2}{21}[/tex]
To find out which one is bigger, we need a common denominator. The LCM of 7 and 21 is 21, so convert the first fraction into a denominator of 21. 7 goes into 21 three times, multiply this to the numerator and denominator:
[tex]\sf\dfrac{1}{7}\rightarrow\dfrac{1\times 3}{7 \times 3}\rightarrow\dfrac{3}{21}[/tex]
Now just compare the numerators to see which one is bigger.
[tex]\sf\dfrac{3}{21}>\dfrac{2}{21}[/tex] therefore, [tex]\sf\dfrac{4}{7}\times\dfrac{1}{4}>\dfrac{4}{7}\times\dfrac{1}{6}[/tex]