Question

Peanuts worth $1.50 per pound were mixed w/ cashews worth $2.25 a pound. How many pounds of each were used if there're 20 pounds at $1.80 per pound?

Answer 1

x=pounds of peanuts y=pounds of cashews
we set up a system of equations:
1.50x+2.25y=20(1.80)
and x+y=20
1.5x+2.25y=36
we can set x to equal 20-y and substitute
1.5(20-y)+2.25y=36
30-1.5y+2.25y=36
.75y=6
y=8
if y=8 then x=12, so there are 12 pounds of peanuts and 8 pounds of cashews