Answer:
The quantity of coffee costing $4 a pound in the coffee mixture is 2 pounds.
Step-by-step explanation:
Given: Coffee costing $4 a pound is mixed with 3 pounds of coffee costing 4.50 a pound to obtain a mixture costing $4.30 a pound.
We have to find the quantity of coffee costing $4 a pound in the mixture.
Let x represent the number of pounds of $4 coffee.
Cost of one pound = 4x.
Cost of 3 pounds of coffee costing 4.50 a pound = 3(4.50)
Cost of mixture costing $4.30 a pound = (x+3)(4.30)
According to given problem,

Solving for x, we get,

Rearranging like term together, we get,



Thus, the quantity of coffee costing $4 a pound in the coffee mixture is 2 pounds.