Question 83248
Let x=amount of 3.50 coffee

Then 100-x=amount of 4.75 coffee

Now we know that the total cost of the 3.50 coffee (3.50x) plus the total cost of the 4.75 coffee(4.75)(100-x) must equal the total cost of the final mixture (4.00(100)).  So our equation to solve is:

3.50x+4.75(100-x)=4.00(100)  get rid of parens

3.50x+475-4.75x=400  subtract 475 from both sides

3.50x+474-475-4.75x=400-475  collect like terms

-1.25x=-75  divide both sides by -1.25
x=60 lbs -------------------------------amount of 3.50 coffee

100-x=100-60=40 lb------------------------amount of 4.75 coffee

CK
3.50(60)+4.75(40)=4.00(100)
210+190=400
400=400


Hope this helps----ptaylor