a health store wants to make a trail mix with raisins and granola. The owner mixes granola, which costs $4 per pound, and raisins, which costs $2 per pound, together to make 25 lbs of trail mix. How many pounds of raisins should he include if he wants the mixture to cost him a total of $80? Solution a= pounds of granola b= pounds of raisins $4/pound of granola $2/pound of raisins 1) a+b=25 pounds 2) ($4/pound of granola)*a + ($2/pound of raisins)*b = $80 3) [solve 2) for b] => ($2/pound of raisins)*b = $80 - ($4/pound of granola)*a 4) b = 40 - 2a insert 4) into 1) 5) a + 40 - 2a = 25 a = 15 pounds of granola <----- insert 6) into 1) b = 10 pounds of raisins <----- .