Question 260069
Coffee counters charge $9.00 per pound for roast coffee and $8.00 per pound for Sumatran coffee. How much of each type should be used to make a 20lb blend that sells for $8.40 per lb?!

Let x  be the number of pounds of the $9.00 coffee and y the amount of $8.00 coffee in the blend.

We know then that 1.) x + y = 20 and

2.) 9.00*x + 8.00*y = 20*8.40

Substitute x = 20 - y from equation 1.) in equation 2.):

9*(20-y) + 8*y = 16.8

Solve the above for y then calculate x = 20-y.