\documentclass [12pt]{article}
\usepackage {multicol}


\begin{document}
Calcula:
\begin{multicols}{4}
\begin{enumerate}
\item \[ \frac{8}{5}\,\cdot \,\frac{10}{3}\,\cdot \,15
\]
\item
\[
\left( {\frac{3}{7}} \right)\,\cdot \,\frac{14}{2}\,\cdot \,\frac{5}{3}
\]
\item
\[
\frac{3}{8}\,\cdot \,\frac{2}{3}\,\,:\,\,\frac{15}{7}
\]
\item
\[
\frac{3}{8}\cdot \frac{5}{8}\,\cdot \,\frac{1}{6}
\]
\item
\[
\frac{45}{15}:\frac{51}{12}
\]
\item
\[
\frac{31}{12}\cdot \frac{75}{21}\cdot \frac{74}{15}
\]
\item
\[
\frac{6}{3}\,\cdot \,\frac{115}{2}\,\cdot \,10
\]
\item
\[
\left( {\frac{6}{7}} \right)\,\cdot \,\frac{18}{5}\,\cdot \,\frac{6}{2}
\]
\item
\[
\frac{6}{9}\,\cdot \,\frac{5}{8}\,\,:\,\,\frac{16}{6}
\]
\item
\[
\frac{2}{9}\cdot \frac{5}{9}\,\cdot \,\frac{2}{6}
\]
\item
\[
\frac{52}{16}:\frac{58}{19}
\]
\item
\[
\frac{25}{14}\cdot \frac{86}{19}\cdot \frac{36}{14}
\]
\item
\[
\frac{12}{4}\,\cdot \,\frac{9}{6}\,\cdot \,16
\]
\item
\[
\left( {\frac{8}{10}} \right)\,\cdot \,\frac{21}{6}\,\cdot \,\frac{3}{9}
\]
\item
\[
\frac{6}{14}\,\cdot \,\frac{8}{5}\,\,:\,\,\frac{16}{5}
\]
\item
\[
\frac{6}{5}\cdot \frac{10}{20}\,\cdot \,\frac{3}{5}
\]
\item
\[
\frac{6}{7}:\frac{26}{18}
\]
\item
\[
\frac{24}{16}\cdot \frac{48}{26}\cdot \frac{75}{9}
\]
\item
\[
\frac{6}{3}\,\cdot \,\frac{12}{5}\,\cdot \,25
\]
\item
\[
\left( {\frac{7}{9}} \right)\,\cdot \,\frac{9}{8}\,\cdot \,\frac{4}{5}
\]
\item
\[
\frac{6}{4}\,\cdot \,\frac{1}{6}\,\,:\,\,\frac{10}{15}
\]
\item
\[
\frac{7}{8}\cdot \frac{4}{6}\,\cdot \,\frac{2}{10}
\]
\item
\[
\frac{32}{41}:\frac{14}{26}
\]
\item
\[
\frac{24}{17}\cdot \frac{57}{65}\cdot \frac{41}{48}
\]
\item
\[
\frac{10}{5}\,\cdot \,\frac{6}{8}\,\cdot \,20
\]
\item
\[
\left( {\frac{9}{3}} \right)\,\cdot \,\frac{12}{6}\,\cdot \,\frac{2}{6}
\]
\item
\[
\frac{7}{10}\,\cdot \,\frac{3}{5}\,\,:\,\,\frac{14}{5}
\]
\item
\[
\frac{8}{10}\cdot \frac{6}{6}\,\cdot \,\frac{4}{11}
\]
\item
\[
\frac{43}{32}:\frac{54}{18}
\]
\item
\[
\frac{14}{22}\cdot \frac{72}{35}\cdot \frac{55}{10}
\]
\item
\[
\frac{9}{18}\,\cdot \,\frac{17}{5}\,\cdot \,9
\]
\item
\[
\left( {\frac{6}{16}} \right)\,\cdot \,\frac{18}{7}\,\cdot \,\frac{4}{2}
\]
\item
\[
\frac{4}{8}\,\cdot \,\frac{3}{1}\,\,:\,\,\frac{19}{6}
\]
\item
\[
\frac{6}{7}\cdot \frac{4}{8}\,\cdot \,\frac{3}{10}
\]
\item
\[
\frac{40}{12}:\frac{50}{9}
\]
\item
\[
\frac{3}{2}\cdot \frac{76}{25}\cdot \frac{32}{11}
\]
\end{enumerate}
\end{multicols}





\end{document}