Answer:
Step-by-step explanation:
Let x represents the number of nights Jack worked and y represents the number of nights Diane worked.
1. The number of nights Diane is scheduled to work is no more than four times the number of nights Jack is scheduled to play. Then
2. Diane will work at least 10 times before the concert. Then
3. Jack earns $50 per night that he plays, then he earned $50x in x nights. Diane earns $25 each night she works, then she earns $25y in y nigths. They need at least $750, so
4. We get the following set of constraints to model the problem: