Hello,
I)
\(\dfrac{2}{5}=\dfrac{2*9*7}{5*9*7}=\dfrac{126}{315}\)
\(\dfrac{4}{9}=\dfrac{4*5*7}{315}=\dfrac{140}{315}\)
\(\dfrac{3}{7}=\dfrac{3*5*9}{315}=\dfrac{135}{315}\)
or
\(\dfrac{126}{315}\leq\dfrac{135}{315}\leq\dfrac{140}{315}\)
thus
\(\dfrac{2}{5}\leq\dfrac{3}{7}\leq\dfrac{4}{9}\)
II)
\(\dfrac{\dfrac{1}{2}+\dfrac{5}{6}}{2}=\dfrac{8}{6*2}=\dfrac{2}{3}\)
