Answer : The number of tablets given should be, 0.5
Explanation :
We are given :
Mass of sulfa drug for a patient = 0.024 g
Total mass of tablets = 12 mg = 
(Conversion factor: 1 g = 1000 mg)
To calculate the number of tablets, we divide the total mass of tablets to the mass of sulfa drug for a patient.

Putting values in above equation, we get:

Hence, the number of tablets given should be, 0.5