Question

Answer 1

\(1;\Leftrightarrow3x+9y=16\)

\(\Leftrightarrow x=\dfrac{16}{3}-3y;\Leftrightarrow y=\dfrac{16}{9}-\dfrac{x}{3}\)

Answer 2

2/

\(\Leftrightarrow5x+6y=15\)

\(\Rightarrow\left\{{}\begin{matrix}x=3-\dfrac{6y}{5}\\y=\dfrac{5}{2}-\dfrac{5x}{6}\end{matrix}\right.\)

Answer 3

3/

\(\Leftrightarrow\dfrac{3}{x}+\dfrac{4}{y}=15\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=\dfrac{3y}{15y-4}\\y=\dfrac{4x}{3\left(5x-1\right)}\end{matrix}\right.\)