A school bought pens, each costing $1, and pencils, each costing $0.5. The cost of the whole purchase was $220. How many pens and pencils were purchased if there were 80 more pencils than pens?

The number of pens = 120 and the number of pencils = 200

Step-by-step explanation:

Let the number of pens x, and the number of pencils is y

the cost of one pen $1, and the cost of one pencil $0.5

The cost of the whole purchase was $220

1 * x + 0.5 * y = 220

x + 0.5 y = 220 ⇒ eq.(1)

there were 80 more pencils than pens

y - x = 80 ⇒ eq.(2)

from eq.(2) x = y - 80

By substitution with x from the last equation at eq.(1)

∴ (y - 80) + 0.5 y = 220

1.5y = 220 + 80 = 300

y = 300/1.5 = 200

x = y - 80 = 200 - 80 = 120

So, the number of pens = 120 and the number of pencils = 200

if you mean

then it's c. 8, -7/3

but if you mean

then it is

answer: a) (0,0), (1,1), (2,8), and (3,27).

step-by-step explanation:

0^3=0

1^3=1

2^3=8

3^3=27

in effect, the exponential equation for this would me y=3^x. each x-coordinate cubed is giving the y coordinate, so a is your answer : )