Ellen wishes to mix candy worth $1.65
per pound with candy worth $3.71 per pound to form 35 pounds of a mixture worth $2.77 per pound. How many pounds of the more expensive candy should she use?
If there are x lbs of the expensive candy, then the rest (35-x) is the cheap stuff. So now just add up the value of the parts to make it equal to the value of the whole:
3.71x + 1.65(35-x) = 2.77(35)