Your mixture of raisins and peanuts is worth $1.40/lb.
You can determine the pounds of raisins from the given information by creating an equation like this:
(lbs raisins)($1.50/lb) + (10lbs peanuts)($1.20/lb) = (lbs raisins + 10lbs peanuts)($1.40/lb)
which looks like this:
1.5r + 12 = 1.4r +14
r = 20
You need 20 lbs of raisins for your mixture.
