Question

15 patients is 50% of what number of patients?

Answer 1

1% of n is equal to n/100

50% of n is therefore just 50*n/100, which is said to equal 15 ...

50n/100 = 15, solve for n

Answer 2

when you say that "15 patients is 50% of all the patients" you are saying "15 patients is ½ of all the patients"

let x be the number of all patients
so if 15=½ x then x=30.