In a certain Algebra 2 class of 26 students, 18 of them play basketball and 7 of them play baseball.

In a certain Algebra 2 class of 26 students, 18 of them play basketball and 7 of them play baseball. There are 5 students who play neither sport. What is the probability that a student chosen randomly from the class plays both basketball and baseball?

Students play either basketball only, baseball only, both sports, or no sports. Let the students who play both sports be b. We have:
b + 18 + 7 - 5 = 26 <-- We subtract 5 because we don't want to double count the students who played a sport who were counted already

We type this equation into our search engine and get:
b = 6