Gọi 3 phân số cần tìm là \(\dfrac{a}{b};\dfrac{a}{b}+d;\dfrac{a}{b}+2d\)
Theo đề bài ta có:
\(\dfrac{\dfrac{a}{b}+\dfrac{a}{b}+d+\dfrac{a}{b}+2d}{3}=\dfrac{3\left(\dfrac{a}{b}+d\right)}{3}=\dfrac{a}{b}+d=\dfrac{2}{5}\)
\(\dfrac{a}{b}+2d-\dfrac{a}{b}=2d=\dfrac{1}{3}\\ \Rightarrow d=\dfrac{1}{3}:2=\dfrac{1}{6}\\ \Rightarrow\dfrac{a}{b}=\dfrac{2}{5}-\dfrac{1}{6}=\dfrac{7}{30}\\ \dfrac{a}{b}+2d=\dfrac{7}{30}+\dfrac{1}{3}=\dfrac{17}{30}\)
Vậy 3 số cần tìm là \(\dfrac{7}{30};\dfrac{2}{5};\dfrac{17}{30}\)