Entropy is a state function! By the state postulate (and/or the Gibbs phase rule), it is uniquely determined once we know enough information (intensive variables) to fix the system's state.
Use tables to calculate entropy changes
Superheated water vapor at a pressure of 200bar, a temperature of 500C, and a flow rate of 10 kg/s is brought to a saturated vapor state at 100bar by mixing it adiabatically with a stream of liquid water at 20C and 100bar. The flow rate of the liquid is 1.95 kg/s. What is the rate of entropy generation?