A magazine costs $3 and a book cost $7 if you want to spend exactly $45 on reading this month and you need to buy eight magazines how many books can you buy write an equation in standard form modeling the situation then see how many books you can buy let em represent the number of magazines you buy and B represents the number of books you buy.

m = 8 and b = 3 OR m = 15 and b = 0

Step-by-step explanation:

Note that the conditions on this problem could be contradictory (they are likely not, but could be)

let m be the number of magazines bought

let b be the number of books, then

3m is the cost of the magazines bought and

7b is the cost of the books bought, since $45 exactly must be spent then

3m + 7b = 45

Let us assume m = 8 and see what happens

3(8)+7b = 45

24+7b=45

7b=21

b=3, this meets the requirements and results in an integer (whole) number of books, if b had ended up as a fraction, then m=8 would have to be wrong and we would have tried m=9 , then 10, 11, 12, up to 15 if necessary until we got a whole number of books.  Notice that 15 magazines and 0 books also works

answer: .64

step-by-step explanation

set up the formula for standard deviation for this set of numbers, then simplify