Answer: 21 pounds of type A coffee were used.
Step-by-step explanation:
Let x represent the number of pounds of type A coffee that were used in the blend.
Let y represent the number of pounds of type B coffee that were used in the blend.
Type A coffee costs Elsa $5.70 per pound, and type B coffee costs $4.30 per pound. The mixture sold for a total cost of $300.30. It means that
5.7x + 4.3y = 300.3- - - - - - - - - - -1
This month's blend used twice as many pounds of type B coffee as type A. It means that
y = 2x
Substituting y = 2x into equation 1, it becomes
5.7x + 4.3 × 2x = 300.3
5.7x + 8.6x = 300.3
14.3x = 300.3
x = 300.3/14.3
x = 21