Bài 4:
Số gà mái là:
15 : \(\dfrac{5}{7}\) = 21 (con)
Đ/S:...
Bài 3 :
a. \(\dfrac{3}{7}+\dfrac{2}{3}+\dfrac{1}{6}=\dfrac{18}{42}+\dfrac{28}{42}+\dfrac{7}{42}=\dfrac{53}{42}\)
b. \(\dfrac{4}{5}-\dfrac{1}{3}-\dfrac{4}{9}=\dfrac{36}{45}-\dfrac{15}{45}-\dfrac{20}{45}=\dfrac{1}{45}\)
c. \(\dfrac{3}{8}\times\dfrac{3}{2}:6=\dfrac{9}{16}:6=\dfrac{9}{16}\times\dfrac{1}{6}=\dfrac{3}{32}\)
d. \(\dfrac{6}{9}:\dfrac{2}{5}\times\dfrac{1}{3}=\dfrac{6}{9}\times\dfrac{5}{2}\times\dfrac{1}{3}=\dfrac{5}{9}\)


