A co-ed gym class has 50 students. Some are left-handed and some are right-handed (of course). If 23 students are boys, 36 students are right-handed, and there are 4 left-handed girls, then how many right-handed boys are there?
If there are 23 boys, then there are 27 girls. If 4 girls are left-handed, then 23 girls are right-handed. So there are 36 – 23 = 13 right-handed boys.