Ответ:

а) 30;

б) 1/1800

Пошаговое объяснение:

[tex]a) \frac{3 \frac{1}{8} + 2 \frac{1}{12} - \frac{1}{3} }{7.3 - 0.4 \times 8.5} = \frac{ \frac{25}{8} + \frac{25}{12} - \frac{1}{3} }{7.3 - 3.4} = \frac{\underbrace{ \frac{25}{8} } _{3} + \underbrace{ \frac{25}{12} } _{2} - \underbrace{ \frac{1}{3} } _{8} }{ 3.9} = \frac{75 + 50 - 8}{3.9} = \frac{117}{3.9} = \bf30[/tex]

[tex]b) \frac{12 \times 0.8 - 1.8}{2 \frac{1}{12} + 2 \frac{1}{15} - \frac{1}{4} } = \frac{9.6 - 1.8 }{ \frac{25}{12} + \frac{31}{15} - \frac{1}{4} } = \frac{7.8}{ \underbrace{ \frac{25}{12} } _{5} +\underbrace{ \frac{31}{15} } _{4} - \underbrace{ \frac{1}{4} } _{15}} = \frac{7.8}{ \frac{125 + 124 - 15}{60} } = \frac{7.8}{ \frac{234}{60} } = \frac{7.8}{234} \times \frac{1}{60} = \frac{1}{30} \times \frac{1}{60} = \bf \frac{1}{1800} [/tex]