9 because it's 3 boys to every 8 girls with 33 in the class together. so start with 6 boys which is 3+3 meaning there will be 16 girls being 8+8. together that makes 22 students then add another 3 boys bumps the total number up to 25 and for those 3 you need 8 girls which bumps 25 up to 33 meaning that in a class of 33 there will be 9 boys altogether