а)
\[ 1,36 : 1,7 = \frac{136}{100} : \frac{17}{10} = \frac{136}{100} \times \frac{10}{17} = \frac{136}{10 \times 17} = \frac{8 \times 17}{10 \times 17} = \frac{8}{10} = 0,8 \]
\[ 6,5 - 0,16 - 0,8 + 1,3 = 6,34 - 0,8 + 1,3 = 5,54 + 1,3 = 6,84 \]
Ответ: 6,84
б)
\[ \frac{3}{7} : \frac{4}{3} = \frac{3}{7} \times \frac{3}{4} = \frac{9}{28} \]
\[ \frac{1}{3} = \frac{1 \times 28}{3 \times 28} = \frac{28}{84} \]
\[ \frac{9}{28} = \frac{9 \times 3}{28 \times 3} = \frac{27}{84} \]
\[ \frac{1}{3} = \frac{1 \times 28}{3 \times 28} = \frac{28}{84} \]
\[ \frac{28}{84} + \frac{27}{84} - \frac{28}{84} = \frac{28 + 27 - 28}{84} = \frac{27}{84} = \frac{9}{28} \]
Ответ: $$\frac{9}{28}$$