a, \(\dfrac{2}{3}x\dfrac{5}{7}+\dfrac{2}{7}x\dfrac{2}{3}\)
\(=\dfrac{2}{3}x\left(\dfrac{5}{7}+\dfrac{2}{7}\right)\)
\(=\dfrac{2}{3}x1\)
=\(\dfrac{2}{3}\)
b, \(\dfrac{3}{4}x\dfrac{8}{15}x\dfrac{10}{22}x\dfrac{11}{3}\)
\(=\left(\dfrac{3}{4}x\dfrac{8}{15}\right)x\left(\dfrac{10}{22}x\dfrac{11}{3}\right)\)
\(=\dfrac{2}{5}x\dfrac{5}{3}\)
\(=\dfrac{2}{3}\)