Question

There were 24 cookies in the first batch and an unknown number of cookies in the second batch. If each student in a class of 22 students was given a cookie and there are 27 cookies left, how many cookies were in the second batch?

Answer 1

Okay, so the total cookies is given by 22 cookies (the ones given to the students) plus 27 cookies (the ones left over) Therefore there were 49 cookies in total. Subtract the 24 cookies from the first batch, and you have 25 cookies remaining, which is the total from the second batch. 

25 cookies.

Answer 2

24 cookies in the first batch
Unknown in the second, let's call it "x".
The total amount of cookies is the amount of cookies eaten by students (22) as well as the amount left (27).
We can set these equivalent to one another:
24+x=22+27
24+x=49
subtract 24 from both sides
24+x=49
-24     -24
x=25
So, there were 25 cookies in the second batch.