You buy bottled water in 12 - packs that cost $3 each. If u drink 3 bottles per day, what is your cost per week?

Cost of bottles that come in packs of 12 = 3 dollars

It is already given in the question that i drink 3 bottles per day. So the cost of 3 bottles has to be determined first and then the number of bottles that is drunk in a week also has to be determined. after that the cost per week can be easily determined.

Number of bottles drunk per day = 3

So

The number of bottles drunk in a week = (3 * 7) bottles

= 21

Now

Cost of a pack of 12 bottles = 3 dollars

Then

Cost of 1 bottle = (3/12) dollars

= (1/4) dollars

= 0.25 dollars

So

The cost of 21 bottles = (21 * 0.25) dollars

= 5.25 dollars

So the cost per week as determined above is $5.25.