This is a fifth grade class
You can solve this problem by using a proportion, comparing absent students to total students.
absent 12 1
total x = 10 (the equal sign is supposed to be in the middle, but I can't do that here)
In a proportion, the cross products are equal. That is:
12 * 10 = 1 * x
120 = x
There are 120 students in the class.