\[\boxed{\mathbf{3.}\mathbf{42}\mathbf{.ОК\ ГДЗ - домашка\ на\ }5}\]
\[\textbf{а)}\ 57 + 12 = 69\ :3 = 23 - 16 =\]
\[= 7 \cdot 14 = 98\ :2 = 49 + 8 = 57\]
\[\textbf{б)}\ 25 \cdot 4 = 100 - 79 = 21 \cdot 3 =\]
\[= 63 - 31 = 32\ :4 = 8 + 17 =\]
\[= 25\]