\begin{array}{r} 7,8 \\\times\ 6 \\\hline 46,8\end{array}

`7,8 xx 6 = 46,8`

`-------`

\begin{array}{r} 0,72 \\\times\ 50 \\\hline 36\end{array}

`0,72 xx 50 = 36`

`-------`

\begin{array}{r} 5,4 \\\times\ 39 \\\hline 486 \\ +162\ \\\hline 210,6\end{array}

`5,4 xx 39 = 210,6`

`-------`

\begin{array}{r} 3,16 \\\times\ 41 \\\hline 316 \\ +1264\ \\\hline 129,56 \end{array}

`3,16 xx 41 = 129,56`