[tex]( - 3.2 + 6.8) \div (2 \frac{1}{12} + 5 \frac{2}{3} ) = \frac{72}{155} \\ 1) \: - 3.2 + 6.8 = 3.6 \\ 2) \: 2 \frac{1}{12} + 5 \frac{2}{3} = 2 \frac{1}{12} + 5 \frac{8}{12} = 7 \frac{9}{12} = 7 \frac{3}{4} \\ 3) \: 3.6 \div 7 \frac{3}{4 } = \frac{18 \times 4}{5 \times 31} = \frac{72}{155} [/tex]