Answer: 6 pounds of French roast coffee and 14 pounds of Sumatran coffee was used.
Step-by-step explanation:
Let x represent the number of pounds of French roast coffee that should be added in the blend.
Let y represent the number of pounds of Sumatran coffee that should be added in the blend.
The total number of pounds of the mixture made is 20 lb. This means that
x + y = 20
The mixture sells for $8.30 a pound. The total cost of the mixture would be
8.3 × 20 = 166
This means that
9x + 8y = 166 - - - - - - - - -1
Substituting x = 20 - y into equation 1, it becomes
9(20 - y) + 8y = 166
180 - 9y + 8y = 166
- 9y + 8y = 166 - 180
- y = - 14
y = 14
x = 20 - y = 20 - 14
x = 6