\[\boxed{\text{5.326.}}\]
\[\textbf{а)}\ n + m = 5\]
\[n = 5 - m\]
\[m = 5 - n\]
\[\textbf{б)}\ b - a = 5\]
\[a = 5 - b\]
\[b = 5 + a\]
\[\textbf{в)}\ 5 \cdot y = x\]
\[y = x\ :5\]
\[5 = x\ :y\]
\[\textbf{г)}\ c\ :5 = z\]
\[c = z \cdot 5\]
\[5 = c\ :z\]