You have 1 case of soap bars and there are 150 bars in a case. you use 300 bars of soap per day. how many cases do you need to order to have enough for 7 days? *

14 cases

Explanation:
First, we will need to find the number of cases needed per day:
We know that one case includes 150 bars and that the daily consumption is 300 bars. To know the number of cases needed daily, we will use cross multiplication as follows:
1 case .............> 150 bars
?? cases .........> 300 bars
number of cases needed daily = 
number of cases needed daily = 2 cases

Then, we will get the number of cases needed weekly (7 days):
We know that 2 cases are needed daily. To know the number of cases needed weekly (7 days), we will simply use cross multiplication as follows:
1 day .............> 2 cases
7 days ...........> ?? cases
number of cases needed weekly = 
number of cases needed weekly = 14 cases

Hope this helps :)