Coffee café mix 90 pounds of coffee that cost six dollars per pound the types of coffee used to make this makes you cost seven dollars and four dollars per pound how many pounds of the seven dollar per pound coffee should be used in this mixture

y =  60

Step-by-step explanation:

From the  information we get:

x  quantity of 4 dollars  coffee used in the mix

y  quantity of 7 dollars  coffee used in the mix

For the quantity of coffee to be sold a 7 $/pound  ( 90 pounds)

Then  6*90  =  540  $

Therefore

x  +  y  =  90     and

4*x  +  7*y  =  540

A two equations system we solve for x and y

y =  90  -  x

4*x  +  7* ( 90  -  x ) = 540

4*x  +  630 - 7*x  =  540

- 3*x  =  - 90

x = 30 pounds   and

y  =  90  -  30

y  =  60

We should use  60 pounds of the seven $ coffee

(x, y)→(x − 8, y − 7)

step-by-step explanation:

enjoy!

a. she will receive a refund of $278.

step-by-step explanation: