\[\boxed{\mathbf{3.}\mathbf{269}}\]
\[\textbf{а)}\ 37 + 246 + 63 =\]
\[= (37 + 63) + 246 =\]
\[= 246 + 100 = 346\]
\[\textbf{б)}\ 671 + 98 - 71 =\]
\[= (671 - 71) + 98 =\]
\[= 600 + 98 = 698\]
\[\textbf{в)}\ 247 - 44 - 56 =\]
\[= 247 - (44 + 56) =\]
\[= 247 - 100 = 147\]
\[\textbf{г)}\ 50 \cdot 51 \cdot 2 = 50 \cdot 2 \cdot 51 =\]
\[= 51 \cdot 100 = 5100\]
\[\textbf{д)}\ 18 \cdot 8 + 8 \cdot 82 =\]
\[= 8 \cdot (18 + 82) = 8 \cdot 100 =\]
\[= 800\]
\[\textbf{е)}\ 146 \cdot 17 - 46 \cdot 17 =\]
\[= 17 \cdot (146 - 46) = 17 \cdot 100 =\]
\[= 1700\]