During the first day of a heat wave and emergency room had three times as many patients as the day before they were 48 patients seen total over there today. how many patients visited the er on each day

16 patients
In this question, we know that the ER the ratio number of the patient when heat wave compared to yesterday(3 times) and the number of patients today (48 patient).
Since 48 patient of today is 3 times more than yesterday, then the number of patient visit ER each day(without heat wave) is:

Patient when heat wave= 3x normal patient visit
48 patient = 3x Normal patient visit
Normal patient visit = 48/3= 16 patients