Let $R_1$,$R_2$,$R_3$ be connected in parallel! See circuit bellow: 
If $R_1$ increasing at $4\:\frac{\Omega }{s}$, If $R_2$ increasing at $2\:\frac{\Omega }{s}$, If $R_3$ decreases at $16\:\frac{\Omega }{s}$, how fast does is R changing?
I don't know what to do, I feel like my teacher didn't give enough information. Normally we would take the derivative to find the rate of change with respect to time and then substitute values we know. But I don't even have any relationship between $R_1$,$R_2$,$R_3$.
Hint: The relationship for resistance is $R^{-1}=\sum \left(\frac{1}{R_n}\right)$ in a parallel circuit. Knowing this you should be able to take the derivative with respect to time.