Question

Помогите решить 1 номер

Answer 1

$frac{1}{frac{1}{30}+frac{1}{42}}=frac{1}{frac{1}{5*3*2}+frac{1}{7*3*2}}=frac{1}{frac{7}{5*7*3*2}+frac{5}{5*7*3*2}}=frac{1}{frac{12}{210}}=1/frac{12}{210}=1*frac{210}{12}=17.5$