Apencil at a stationery store costs $1, and a pen costs $1.50. shawn spent $12 at the store. he bought a total of 9 items. which system of equations can be used to find the number of pencils (x) and pens (y) he bought?
1.5x + y = 12
x = 9y
x + 1.5y = 12
x + y = 9
x + 9y = 12
x = 1.5y
9x + y = 12
x = 1.5y