Question

A pencil at a stationery store costs $1, and a pen costs $1.50. Stella spent $21 at the store. She bought a total of 18 items. Which system of equations can be used to find the number of pencils (x) and pens (y) she bought? (5 points)

1.5x + y = 21
x = 18y
18x + y = 21
x = 1.5y
x + 1.5y = 21
x + y = 18
x + 18y = 21
x = 1.5y

Answer 1

Medals!

Answer 2

Okay, if a pencil costs $1, and \(x\) represents the number of pencils, how do you write an expression for the amount of money spent on pencils?

Answer 3

i think like the 3rd answer

Answer 4

well, let's figure it out. how do you write the expression for the amount spent on pencils, if a pencil costs $1 and there are \(x\) pencils?

Answer 5

Idk

Answer 6

what is the cost of 1 pencil?

Answer 7

1$

Answer 8

what is the cost of 2 pencils?

Answer 9

2$

Answer 10

what is the cost of 57 pencils? (btw, the $ goes in front)

Answer 11

you get the cost by multiplying the cost of 1 item by the number of items, right?

Answer 12

$57

Answer 13

Im pretty sure the answer is the 3rd one

Answer 14

so the cost of \(x\) pencils when pencils cost $1 each is \(\$1*x\) or \(1x\) or \(x\) if we assume the price is in dollars.

Pens cost $1.50 each. If you have \(y\) pens, how much is that?

Answer 15

1.5y

Answer 16

I agree the answer is C: I'm trying to solidify your understanding of this so you never have to ask again, you'll just know the right answer. Worth a minute or two of your time, right?

Yes, 1.5y is the expression for the cost of the pens.

We know that we spent $21 on \(x\) pencils and \(y\) pens, so how do we write that in an equation?

Answer 17

x + 1.5y=21

Answer 18

Very good. And if we know that we have a total of 18 items, how do we write that?

Answer 19

x + y = 18

Answer 20

Can u help me with one more?

Answer 21

Excellent. For a medal of your own, how many pens and pencils?

Answer 22

18 and 21

Answer 23

The equation 2.2x – 4.4 = 1.8x can be transformed to form which of the following expressions?

4.0x = 4.4
0.4x = –4.4
0.4x = 4.4
4.0x = –4.4

Can u help me with this one?

Answer 24

No, 18 pens and 21 pencils doesn't add up to 18 items, does it?

Answer 25

31

Answer 26

Come on, you aren't thinking. The total number of pens + pencils is 18. The total cost is $21.

Well, whatever. Let's do your other problem.

\[2.2x – 4.4 = 1.8x\]

What happens if you subtract \(1.8x\) from both sides?

Answer 27

2.2x - 2.6

Answer 28

Now what?

Answer 29

so 0.4x in the beginning

Answer 30

\[2.2x-4.4-1.8x=1.8x-1.8x\]\[2.2x-1.8x-4.4 = 0x\]\[0.4x-4.4=0\]
Now we add 4.4 to both sides:
\[0.4x-4.4+4.4=0+4.4\]\[0.4x=4.4\]

Answer 31

Thank you!