\[\boxed{\text{1046.}\text{\ }еуроки - ответы\ на\ пятёрку}\]
\[\textbf{а)}\ 4x - 3y = 12\]
\[- 3y = 12 - 4x\]
\[3y = 4x - 12\]
\[y = \frac{4}{3}x - 4.\]
\[\textbf{б)}\ 4x - 3y = 12\]
\[4x = 12 + 3y\]
\[x = 3 + \frac{3}{4}\text{y.\ }\]