The Osborne Bakers want to make 30 pounds of a berry mix that costs $3.00 per pound to use in their pancake mix. They are using blueberries that cost $2.00 per pound and blackberries that cost $3.50 per pound. How many pounds of blackberries should be used in this mixture?

You have to use 20 pounds of blackberries

Step-by-step explanation:

To start, we are going to make two equations, one that represents the amount of pounds and another that represents the prices

a = blueberries

m = blackberries

a + m = 30

a * 2$ + m * $3.50 = 30 * $3

let's clear in the first equation

a + m = 30

a = 30 - m

we replace in the second equation a by (30 - m)

a * $2 + m * $3.50 = 30 * $3

(30 - m) * 2 + m * 3.50 = 30 * 3

60 - 2m + 3.5m = 90

-2m + 3.5m = 90 - 60

1.5m = 30

m = 30/1.5

m = 20

we replace m with its value in the first equation

a = 30 - m

a = 30 - 20

a = 10