 In this system of structural equations, even after you know that the exogenous variable \(Z = 10\), you are not able to solve for the values of the two endogenous variables, \(X\) and \(Y\). The reason for this is that, in this system of equations, there is a cycle of influence: \(X\) influences \(Y\), and \(Y\) influences \(X\). When there are cycles of influence like this, even a deterministic system of equations, together with an assignment of values to the exogenous variables, will not determine the values of all of the endogenous variables. (See the entry on  backwards causation  and the section on causal loops in the entry on  time travel.)  However, if we rule out cycles of influence like this, then an assignment of values to the exogenous variables will determine the values of all of the variables in the model. Likewise, any probability distribution over the exogenous variables will induce a probability distribution over the endogenous variables, as well.