John has to replace the ball bearings for machines he works with.  He has 10 machines and they take 30 ball bearings each.  It normally costs $1 per ball bearing but right now there is a sale where they are only $.75.  Also since he is buying in bulk he gets a further 20% discount.  How much money did he save by buying them all during the sale rather than 1 at a time?
He needs to replace 30*10=<T>multiply(30, 10)=300 ball bearings
The normal price is 300*1=$<T>multiply(300, 1)=300
Because of the sale he only has to pay 300*.75=$<T>multiply(300, 0.75)=225.0
He then gets a discount which shaves another 225*.2=$<T>multiply(225, 0.2)=45.0 off the price
That means he only pays 225-45=$<T>subtract(225, 45)=180
So he saved 300-180=$<T>subtract(300, 180)=120
