Giải bài 2 trang 168 - SGK Toán lớp 4

a) $\dfrac{2}{7}\times x = \dfrac{2}{3}\\\,\,\,\,\,\,\,\,\,\,\,x = \dfrac{2}{7}:\dfrac{2}{3}\\\,\,\,\,\,\,\,\,\,\,\,x=\dfrac{3}{7}$   

b) $\dfrac{2}{5}: x = \dfrac{1}{3}\\\,\,\,\,\,\,\,\,\,x=\dfrac{2}{5}: \dfrac{1}{3}\\\,\,\,\,\,\,\,\,\,x = \dfrac{6}{5}$         

c) $x : \dfrac{7}{11}= 22\\x \,\,\,\,\,\,\,\,\,\,\,= 22\times \dfrac{7}{11}\\x \,\,\,\,\,\,\,\,\,\,\,=14$