\[\boxed{\mathbf{3.}\mathbf{357}}\]
\[\textbf{а)}\ 34 + 25 = 59\]
\[172 + 28 = 200\]
\[59 + 37 = 96\]
\[4587 + 764 = 5351\]
\[\textbf{б)}\ 57 - 13 = 44\]
\[80 - 34 = 46\]
\[123 - 18 = 105\]
\[10\ 273 - 549 = 9724\]
\[\textbf{в)}\ 24 \cdot 3 = 72\]
\[302 \cdot 7 = 2114\]
\[26 \cdot 37 = 962\]
\[45 \cdot 206 = 9270\]
\[\textbf{г)}\ 35\ :7 = 5\]
\[84\ :4 = 21\]
\[608\ :19 = 32\]
\[2052\ :38 = 54\]