[tex]a) 1\frac{5}{11} + \frac{7}{11}= \frac{16}{11}+ \frac{7}{11} = \frac{23}{11}= 2\frac{1}{11}\\ \\ b) 2\frac{1}{3} + 1\frac{2}{5} = 3+(\frac{1}{3} + \frac{2}{5}) = 3\frac{11}{15}\\ \\ c) 1\frac{4}{11} - \frac{9}{11} = \frac{15}{11} - \frac{9}{11}= \frac{6}{11} \\\\d) 6\frac{7}{15} - 2\frac{2}{5}= 4 + (\frac{7}{15}- \frac{2}{5}) = 4 \frac{1}{15}[/tex]
