How do i find the population equilibrium?

To get specific answer,you should give us more specific definition of variable and equation.R and W are number or rubbit and wolves in an interval of time or what. And RW should be a new variable.It is not "rabitwolves" which will have no meaning. You cannot differentiate both of the two equation subject to t.Because t is not the independent variable.The two equations have no relation except RW which is exogenous variable. It is an recursive equation.