If you can, explain the step by step process into finding the answer.

$6 per lb.

Step-by-step explanation:

Given :

1 lb of blend > costs $7

Assume that we make 3 lbs of blend :

3 lbs of blend > costs $7 x 3 = $21

we are also given that blend is made from a ration of 2: 1 of arabica: robusta,

hence 3 lb of blend will be made out of 2 lbs of arabica and 1 lb of robusta.

Considering the costs:

Cost of 3 lb of blend = cost of 2 lb of arabica + cost of 1lb of robusta

we are given that robusta is $9 for 1 lb,

hence substituting what we know into this equation

$21 = cost of 2 lb of arabica + $9

cost of 2 lb of arabica = $21 - 9 = $12

cost of 1 lb of arabica = $12 / 2 = $6 per lb.