\[\boxed{\mathbf{3.}\mathbf{99}}\]
\[\textbf{а)}\ 29x + 25 = 83\]
\[29x = 83 - 25\]
\[x = 58\ :29\]
\[x = 2.\]
\[\textbf{б)}\ 55\ :z + 19 = 30\]
\[55\ :z = 30 - 19\]
\[z = 55\ :11\]
\[z = 5.\]
\[\textbf{в)}\ 84 - 13x = 19\]
\[13x = 84 - 19\]
\[x = 65\ :13\]
\[x = 5.\]
\[\textbf{г)}\ y\ :6 - 18 = 14\]
\[y\ :6 = 14 + 18\]
\[y = 32 \cdot 6\]
\[y = 192.\]