The operation ○ is defined by the equation x ○ y = (x-y)/(x+y), where y ≠ -x.  If 3 ○ y = 5 ○ 4, then y =

~$\frac{1}{9}$~

~$\frac{4}{15}$~

~$\frac{5}{12}$~

~$\frac{12}{5}$~

~$\frac{15}{4}$~