\[\boxed{\text{139.}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[1)\ 9 \cdot (6 + 3) = 9 \cdot 9 = 81.\]
\[9 \cdot (6 + 3) = 9 \cdot 6 + 9 \cdot 3 =\]
\[= 54 + 27 = 81.\]
\[2)\ 8 \cdot (4 + 5) = 8 \cdot 9 = 72.\]
\[8 \cdot (4 + 5) = 8 \cdot 4 + 8 \cdot 5 =\]
\[= 32 + 40 = 72.\]
\[3)\ 6 \cdot (5 + 2) = 6 \cdot 7 = 42.\]
\[6 \cdot (5 + 2) = 6 \cdot 5 + 6 \cdot 2 =\]
\[= 30 + 12 = 42.\ \]