Вычислите: 1/(1/35-1/60).

\[\frac{1}{\frac{1^{\backslash 12}}{35} - \frac{1^{\backslash 7}}{60}} = \frac{1}{\frac{12 - 7}{420}} = 1\ :\frac{5}{420} =\]

\[= 1 \cdot 84 = 84.\]