Math
posted by Rachel .
Peanuts sell for $3.00 per pound. Cashews sell for $6.00 per pound. How many pounds of cashews should be mixed with 12 pounds of peanuts to obtain a mixture that sells for $4.20 per pound?

C*6+12*3=(C+12)4.20

amount of cashews  x pounds
amount of peanuts  12x pounds
6x + 3(12x) = 4.2(12)
6x + 36  3x = 50.4
3x = 14.4
x = 4.8
need 4.8 pounds of cashews and 7.2 pounds of peanuts
Proof:
6(4.8) + 3(7.2)
= 50.4
cost per pound = 50.4/12 = 4.2 
Ignore my solution
Didn't read the question careful enough
go with bobpursley's solution