You formula is correct
normally it is written as
$$C=\frac{5}{9}(F-32)$$
but your formula is exactly the same. :)
C=(98.6-32)/1.8 = 37 degrees Celcius
$${\frac{\left({\mathtt{98.6}}{\mathtt{\,-\,}}{\mathtt{32}}\right)}{{\mathtt{1.8}}}} = {\mathtt{37}}$$