12 large rafts costs $1200 so subtract that amount from you budget. If you do that you will have $400 left. So I divided $400 by the amount of money each small raft cost whitch was $40 per small raft so i got the quotient of 10.
Sorry if i worded that weirdly but you get the point.
P.s sorry if it isn't comlety correct but i did my best so... ya