Question 14619
Ok, let x = the number of lbs of premium coffee at $6 per lb. Then (100 - x) = the number of lbs of regular coffee at $4 per lb. So you need the sum of these to make 100 lbs of blended coffee at $4.64 per lb.

Here's the equation:

x($6) + (100-x)($4) = 100($4.64) Simplify and solve for x, the number of lbs of premium coffee.

6x + 400 - 4x = 464
2x + 400 = 464 Subtract 400 from both sides.
2x = 64 Divide both sides by 2
x = 32 lbs of premium coffee. 

100 - x = 100 - 32 = 68 lbs of regular coffee.

Check:

32(6) + 68(4) = 100(4.64)
192 + 272 = 464
464 = 464 Ok.