how many pounds of nuts selling for 9 per lb and raisins for

how many pounds of nuts selling for $9 per lb and raisins for $3 per lb should a person combine to obtain 120 lb of a trail mix selling for $5 per lb ?

Solution

let number of pounds of nuts =x , raisins =y

120 lb of a trail mix => x+y =120

=>y=120-x------>(1)

nuts selling for $9 per lb and raisins for $3 per lb are combined to obtain 120 lb of a trail mix selling for $5 per lb

9x + 3y =5*120

9x + 3y =600------->(2)

substitute (1) in (2)

9x + 3(120-x) =600

9x +360 -3x =600

6x =600-360

6x=240

x=40

y=120-x

y=120-40

y=80

so number of pounds of nuts =x=40 , raisins =y=80 the person should combine