Bài 1: Tính: a) \(\frac{2}{7}\) + \(\frac{4}{7}\) ; \(\frac{6}{7}\) - \(\frac{2}{7}\) ; \(\frac{6}{7
Bài 2: Tính : a) \(\frac{2}{7}\) + \(\frac{3}{5}\) ; \(\frac{31}{35}\) - \(\frac{2}{7}\) ; \(\frac{3
Bài 3: Tìm x : a) \(\frac{2}{9}\) + x = 1; b) \(\frac{6}{7}\) - x = \(\frac{2}{3}\) ; c) x - \(\frac