If 150 students dislike soda, how many students like soda?
800 - 150 = 650
650 students out of 800 like soda. How many students are attending the school dance?
400 students are attending the school dance. How many of those 400 students are expected to like soda?
Since 650 students out of 800 that like soda, we can set up a proportion to find the expected number of students at the dance that will like soda.
x = 325 students