Question 148915
x=# pounds of cashews
y=# pounds of peanuts


5x+2y=63--------------Because the cost of it all is 21 times 3 (21 pounds of a mixture that sells for $3.00 per pound)


x+y=21


So you have two equations
5x+2y=63
x+y=21


Solve for x in the second equation
x=21-y


Plug that into the first equation
5(21-y)+2y=63


Distribute
105-5y+2y=63


Combine like terms
105-3y=63


Subtract 105 from both sides
-3y=-42


Divide by -3
y=14


That is the pounds of peanuts
plug that into the second equation
x+14=21


Subtract 14 from both sides
x=7


That is the pounds of cashews
So,


14 lbs. peanuts
7 lbs. cashews