Đáp án:
a) `2\frac{1}{5} × 3\frac{4}{9} = \frac{11}{5} × \frac{31}{9} =\frac{11×31}{5×9} =\frac{341}{45}`
b) `7\frac{2}{3} : 2\frac{1}{4} = \frac{23}{3} : \frac{9}{4} = \frac{23}{3} × \frac{4}{9} = \frac{23×4}{3×9} = \frac{92}{27}`
c) `4\frac{2}{3} + 2\frac{3}{4} × 7\frac{3}{11} = \frac{14}{3} + \frac{11}{4} × \frac{80}{11} = \frac{14}{3} + 20 = \frac{14}{3} + \frac{60}{3} = \frac{74}{3}`
