Apencil 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? x + 18y = 21 x = 1.5y 18x + y = 21 x = 1.5y x + 1.5y = 21 x + y = 18 1.5x + y = 21 x = 18y

Let x represent represent the amount of pencils that Stella bought, and y represent that number of pens that Stella bought.

We know that Stella bought 18 items total, meaning that the number of pencils and pens must equal 18 or :

x + y = 18

Additionally, we know that she spent $21, and that each pencil costs $1, and that each pen costs $1.50.  Therefore, 

1x + 1.5y = 21

So, the system of equations that can be used to find the number of pencils (x) and the pens (y) she bought would be:

x + 1.5y = 21
and 
x + y = 18