`#3107.101107`
a)
\(x\times\dfrac{4}{5}\div2=\dfrac{6}{7}\\x\times\dfrac{2}{5}=\dfrac{6}{7}\\ x=\dfrac{6}{7}\div\dfrac{2}{5}\\ x=\dfrac{15}{7} \)
Vậy, \(x=\dfrac{15}{7}\)
b)
\(\dfrac{6}{5}\div x\div\dfrac{5}{4}=\dfrac{10}{15}\\ \dfrac{24}{25}\div x=\dfrac{10}{15}\\ x=\dfrac{24}{15}\div\dfrac{10}{15}\\ x=\dfrac{36}{25}\)
Vậy, \(x=\dfrac{36}{25}.\)