Use separation of variables to find the solution to the differential equation $\frac{dP}{dt}=0.06P$ if $P(0)=90$.
$$P(t)=$$

Step 1 ：This is a simple first order differential equation. The general solution to such an equation is given by the formula $P(t)=P(0)\ast e^{kt}$, where $P(0)$ is the initial condition, $k$ is the rate of growth, and $t$ is time. In this case, $P(0)=90$ and $k=0.06$. We can substitute these values into the formula to find the solution.

Step 2 ：Now that we have the function defined, we can use it to find the population at any given time. For example, if we want to find the population at time $t=10$, we can simply call the function $P(10)$.

Step 3 ：The solution to the differential equation $\frac{dP}{dt}=0.06P$ with initial condition $P(0)=90$ is $P(t)=90\ast e^{0.06t}$. For example, at time $t=10$, the population is approximately $\boxed{{\displaystyle 163.99}}$.