\[\boxed{\mathbf{3.}\mathbf{276}}\]
\[\textbf{а)}\ 100 - 55 = 45 \cdot 2 =\]
\[= 90\ :18 = 5 \cdot 15 = 75\]
\[\textbf{б)}\ 90 - 71 = 19 \cdot 3 = 57 + 23 =\]
\[= 80\ :16 = 5\]
\[\textbf{в)}\ 100 - 54 = 46\ :23 = 2 \cdot 19 =\]
\[= 38 + 22 = 60\]
\[\textbf{г)}\ 100 - 13 = 87\ :3 =\]
\[= 29 + 27 = 56\ :14 = 4\ \]