Hello Nevaeh,
Rafael reads a book at a rate of 12 chapters per hour. It means for every hour, he reads 12 chapters.
So number of chapters read = 12 * (number of hours)
So, in 2 hours, he will read 12 * 2 = 24 chapters.
From there, you can figure out how many chapters he will read in three (3) hours.
Cheers.