7. At the conference. $85 \%$ of the delegates at the conference know English, and $75 \%$ know Spanish. What fraction of the delegates know both languages?
7. Note that $85 \%+75 \%=160 \%$, which exceeds the total number of conference delegates by $60 \%$. The excess is due to those people who know both languages - we counted them twice. Thus, not less than $60 \%$ of the conference delegates know both languages.