Hi, I'm having problems understanding this question and I'm not entierly sure what it even means so some help would be really appreciated!

Question:

Using the change of dependent variable: v=e^u, find a second order linear partial differential equation for v(x,t) [This is that I don't understand..what does it mean by "for v(x,t)?] from the following nonlinear partial differential equation for u(x,t):

u_t - (u_x)^2 = u_xx