Agirl scout was selling boxes of cookies. in a month, she sold both boxes of chocolate chip cookies ($1.25 each) and boxes of plain cookies ($0.75 each). altogether, she sold 1585 boxes for a combined value of $1588.75. how many boxes of plain cookies did she sell?

Number of plain cookie boxes sold = 785 boxes

Step-by-step explanation:

Given: Cost of a chocolate chip cookie box = $1.25

Cost of a plain cookie box = $0.75

Total number of boxes sold = 1585

Total cost of the sold boxes = $1588.75

Let, number of plain cookie boxes sold = x

Number of chocolate chip cookie boxes sold = 1585 - x

So,

Total cost = total cost of the sold plain cookie boxes + total cost of the sold chocolate chip cookie boxes

$1588.75 = x ($0.75) + (1585 - x) ($1.25)

1588.75 = 0.75 x + 1981.25 - 1.25 x

0.5 x = 392.5

Therefore,

Number of plain cookie boxes sold: x = 392.5 ÷ 0.5 = 785 boxes