If Rosie is trying to figure out the amount that she needs to pay for her total yoga classes.
First, we need to establish what we know, and what we do not know.
We know that Rosie knows how many yoga classes she has.
We know that she knows how many yoga classes she bought.
She does not know how much each yoga class costs.
So, that cancels out A, B, and C because she doesn't know how much one yoga class costs.
It can only be D, because D tells us that she knows the total is $30, but not the amount each class costs.
3320, 10^3 means move 3 units to the right.
