At lunch, $60\%$ of the students selected soda while $20\%$ selected milk. If 72 students selected soda, how many students selected milk?
I can use the fact that $60\%$ of the students selected soda to do this. If 72 students selected soda, and that is $60\%$ of the total, then I can write an equation: 72 = 0.6x, where x is the total number of students. To solve for x, I need to divide both sides by 0.6. This gives me x = 120. So there were 120 students in total. Now I can use the other given fact, that $20\%$ of the students selected milk. If $20\%$ of 120 students selected milk, then I can multiply 0.2 by 120 to get the number of students who selected milk. This gives me 0.2 * 120 = 24. So 24 students selected milk.

