PLEASE HELP

You are interested in researching whether or not AP biology students who use a test prep book perform better on the exam than those who do not use a test prep book. You take 60 random students and give 30 of them a test prep book, while the other 30 will use the resources they already have. After the students take the exam you analyze the data and find that of the students who used a test prep book, 26 passed. For the students who used only the resources they already had, you found that 12 passed. With this data would you suggest to future students to use a test prep book?

Step 1: state the null hypothesis:

Step 2: determine your expected values:

Step 3: complete the Chi square chart:

Step 4: calculate your degrees of freedom:

Step 5: interpret results:

***I just need to know what the expected value is and why***