1/3 just means divided by 3. So that means that the number of girls times 3 equals the total students. So 12 x 3= 36. 36 is the total number of students in class. To find boys just subtract 12 from 36. 36-12=24. Answer TO PART A is 24. Now for 2nd one, just divide the number of girls by 2. ANSWER TO PART B IS 6