How do you calculate the standard deviation of E when E = D/(D+3.33)

What do you mean by 'E' and 'D'? :confused:

This is an equation. They are just variables. I want to know how to set up to solve for values placed in for "D". One E value is equal to 0.255 and that came from solving the equation E = D/(D+3.33). D has a standard deviation of 0.005. What is the standard deviation of E?