Tomorrow, mrs. wendel's class will be using toothpicks for a science project.  each student must use at least 9 toothpicks for the project.  mrs. wendel knows that there is already a bag of 50 toothpicks in the class storage room.  she plans to buy  x  additional toothpicks this afternoon to make sure her class will have enough. if her class has  30 students, which number sentence represents this situation?