Question 430068
If you have 30lbs of $5 coffee, then your total price should be 30X5, or $150 worth of coffee.  This gives us two equations:

X + Y =30
7X + 2Y= 150

Multiply the first equation by 2, we get
2X+2Y=60

Subtract this equation from the 2nd equation, we get
5X=90
X=18

Therefore we need 18 lbs. of $7 coffee and (30-18)or 12 lbs. of $2 coffee.