\[\boxed{\text{6.313.}}\]
\[\textbf{а)}\ 39,6x + 0,4x - 5,3 = 74,7\]
\[40x = 74,7 + 5,3\]
\[40x = 80\]
\[x = 80\ :40\]
\[x = 2.\ \]
\[Ответ:2.\ \]
\[\textbf{б)}\ 97,3y - 17,3y + 9,3 = 97,3\]
\[80y = 97,3 - 9,3\]
\[80y = 88\]
\[y = 88\ :80\]
\[y = 1,1.\ \]
\[Ответ:1,1.\ \]