She paid $40 each week, hence the "w" next to 40. She then paid $12.50 so both $40w and $12.50 would equal to $492.50. So she paid $492.50 in all for the class.
Now the w would equal, 12. Multiply 40 x 12 and it'd equal 480.
Then you add the additional $12.50 she paid for the registration & it'd equal to $492.50.
