Answer :
[tex]\frac{5}{4}=\frac{x}{12}\ \ \ \ \ |cross\ multiply\\\\4\cdot x=5\cdot12\\\\4x=60\ \ \ \ \ |divide\ both\ sides\ by\ 4\\\\\boxed{x=15}[/tex]
[tex] \dfrac{5}{4} = \dfrac{x}{12} \\ \\4*x=5*12 \\ \\4x=60 \ \ \ /:4 \\ \\x=60:4 \\ \\x=15[/tex]
