What is 3(X+y)÷12x if y=5

I will assume that x and X are meant to be the same.

$$3(x+y)\div 12x \qquad where\:\:y=5\\\\
=3(x+5)\div 12x\\\\
=\dfrac{3(x+5)}{12x}\\\\
\mbox{divide top and bottom by 3}\\\\
=\dfrac{1(x+5)}{4x}\\\\
=\dfrac{x+5}{4x}\\\\$$