A girl 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 1,585 boxes for a combined value of $1,586.25. How many boxes of plain cookies did she sell? Select the correct option:
A) 0
B) 233
C) 500
D) 695
E) 790
Let #plain cookies sold be X then #chocolate cookies = (total cookies-X)   790quating for X   (0.75)*X +(1.25)*(1585-X)=1586.25   =&gt;x=790   790
<result>E</result>
A girl 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 1,585 boxes for a combined value of $1,586.25. How many boxes of plain cookies did she sell?