Ответ:

[tex]\frac{1}{\frac{1}{35} -\frac{1}{60} } =84[/tex]

[tex]1)\frac{1}{35}- \frac{1}{60}=\frac{12}{420} -\frac{7}{420} =\frac{5}{420} =\frac{1}{84}[/tex]

[tex]2)1 : \frac{1}{84} =\frac{1*84}{1}=84[/tex]