Tính: (1 điểm) a)\(\frac{3}{7}\) + \(\frac{4}{9}\) – \(\frac{1}{4}\) = ……………………………………………………………………………………… = ……………………………………………………………………………………… b)\(\frac{1}{6}\) × \(\frac{6}{9}\) – \(\frac{1}\) = ……………………………………………………………………………………… = ………………………………………………………………………………………