If the answer is given in sufficient detail, you deserve the full points. For example, when asking for the states that satisfy a formula E[phi SU psi], you may argue as follows: The fix point iteration would start with the empty set of states, then with the states satisfying psi (you should name them here), and will then add iteratively the predecessors where phi holds (then show the sequences of states added). That should do.

Alternatively, if it is just asked which states satisfy that formula, you may explain so by the semantics of the formulas. However, don't forget to mention why other states then do not satisfy the formula.