# Math

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?

I think it is this: x + 18y = 21
x = 1.5y

18x + y = 21
x = 1.5y

x + 1.5y = 21
x + y = 18

I know for a fact not this: 1.5x + y = 21
x = 18y

1. x = number of pens

y = number of pencils

She bought a total of 18 items.

x + y = 18

Stella spent 21 \$

1.5\$ * x + 1 \$ * y = 21 &

1.5 x + 1 * y = 21

1.5 x + y = 21

You must solve system :

x + y = 18

1.5 x + y = 21

The solutions aree .

x = 6

y = 12

Proof :

6 * 1.5 \$ + 12 * 1 \$ = 9 \$ + 12 \$ = 21 \$

posted by Bosnian
2. OR if you write :

x = number of pencils

y = number of pens

then

x + 1.5 y = 21

x + y = 18

posted by Bosnian

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