The Wiki page about linear dynamical systems says:
linear dynamical systems can be solved exactly
But from what I've found on the web, in the case of linear time-varying dynamical system (e.g. $\mathbf x'=\mathbf A(t)\mathbf x(t)$, where $\mathbf x$ is a n-dimensional state vector and $\mathbf A$ a $n*n$ time varying matrix) a closed form solution is very rare.
Which one of the two sentences is true?