Question 1112776
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<pre>
Let a = # of packs of Coffee A;

    b = # of packs of Coffee B;

    c = # of packs of Coffee C.


Then, counting the balances for each type of coffee beans, you have this system of 3 equations in 3 unknowns a, b and c:


0.3a + 0.2b + 0.1c = 30   (kilograms of Arabica)   (1)  (<<<---=== counting Arabica)

0.2a + 0.1b + 0.2c = 25   (kilogram of Robusta)    (2)  (<<<---=== counting Robusta)

       0.2b + 0.2c = 15   (kilogram of Kenya)      (3)   (<<<---=== counting Kenya)


There are many ways to solve it.


I chose the simplest way, using the online solver of this site

    https://www.algebra.com/algebra/homework/Matrices-and-determiminant/cramers-rule-3x3.solver


giving me the answer a= 65,  b= 30  and  c= 45.


The last step that I did was checking:

    0.3*65 + 0.2*30 + 0.1*45 = 30    ! Correct !

    0.2*65 + 0.1*30 + 0.2*45 = 25    ! Correct !

             0.2*30 + 0.2*45 = 15    ! Correct !
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Solved.