You can use the Solve() function (note the capital S), which is a wrapper for Maxima's solve(). There is a handbook included in the distribution, accessible via the [?] button in the tool bar. In the contents page, find the function index and navigate to Solve() and Assign() in order to see the details. Take care to use Optimization -> None or Symbolic for display of solutions, as they are returned in the form of equations like x = 2.
Martin Kraska
Pre-configured portable distribution of SMath Studio: https://en.smath.info/wiki/SMath%20with%20Plugins.ashx