Clodagh and Eva went school supply shopping together. Clodagh bought 3 packs of pencils and 5 notebooks for a total of $18. Eva bought 4 packs of pencils and 4 notebooks for a total of $16.80. How much does a pack of pencils cost? How much does a notebook cost?

each notebook costs $2.70

each pack of pencils costs $1.50

Step-by-step explanation:

system of equations:

let p = pack of pencils

let n = notebook

3p + 5n = 18

4p + 4n = 16.8

I used the elimination method by multiplying the first equation by 4 and the second equation by -3

4(3p + 5n = 18)  =  12p + 20n = 72

-3(4p + 4n = 16.8)  =  -12p -12n = -50.4

adding the new equations together you get:  8n = 21.6

n = 21.6/8

n = $2.70

solve for 'p':

3p + 5(2.7) = 18

3p + 13.5 = 18

3p = 4.5

p = $1.50

an advantage of the standard deviation is that it increases as the dispersion of the data increases. e. the interquartile range is preferred when the data are not skewed or no have outliers. an advantage of the standard deviation is that it uses all the observations in its computation.

the easiest way to do these would be to solve the equations. if you can solve the equation than you can solve these problems.