In a class 21 of students, 5 have a brother and 14 have a sister. There are 3 students who have a brother and a sister. What is the probability that a student has a sister given that they do not have a brother?

Look, when you want to do something like put it like x^2. x2 could mean x² or x₂. so to clear confusion, know the notation. to find the product multiply the x's and you get -8x and the y's and you get 6y. since it's all being multiplied it is just -8x6y, or answer a. although the better answer is -48xy(combining -8 and 6) because you should multiply constants whenever you can.