Question 1084678
x pounds of $10 a pound coffee
30 pounds of $4 per pound coffee
want (30+x) pounds worth $5 a pound
10x+120=150+5x
5x=30
x=6 pounds 
That is $60 of coffee plus 30 pounds of $4 coffee($120) to have a total of 36 pounds at $5 or $180.