Giải bình thường:
(1)\(\frac{1+3y}{12}=\frac{1+6y}{16}\Leftrightarrow16.\left(1+3y\right)=12.\left(1+6y\right)\) tích trung tỷ = tích ngoại tỷ
\(\Leftrightarrow4.\left(1+3y\right)=3.\left(1+6y\right)\)
\(\Leftrightarrow4+3.4y=3.+6.3y\Leftrightarrow\left(18-12\right)y=4-3=1\)
\(\Rightarrow y=\frac{1}{6}\)
(2)\(\frac{1+6y}{16}=\frac{1+9y}{4x}\Leftrightarrow\frac{2}{16}=\frac{1+\frac{3}{2}}{4x}=\frac{5}{8x}\Rightarrow x=5\)