SOLUTION: The average age of 3 people is 15. If the 3rd person is 5 years older than the 1st person and the 2nd person is 4 years younger than the 1st person, what is the age of the 2nd pers

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Question 828321: The average age of 3 people is 15. If the 3rd person is 5 years older than the 1st person and the 2nd person is 4 years younger than the 1st person, what is the age of the 2nd person?
Answer by TimothyLamb(4379) About Me  (Show Source):
You can put this solution on YOUR website!
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(x + y + z)/3 = 15
z = x + 5
y = x - 4
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put the system of linear equations into standard form:
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x + y + z = 45
x - z = -5
x - y = 4
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copy and paste the above linear system in standard form into this matrix-method solver:
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solution:
x = 14.666667 = 14 + 2/3
y = 10.666667 = 10 + 2/3
z = 19.666667 = 19 + 2/3
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system matrix
1 1 1
1 0 -1
1 -1 0
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inverse of system matrix
0.33333333 0.33333333 0.33333333
0.33333333 0.33333333 -0.66666667
0.33333333 -0.66666667 0.33333333
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determinant of system matrix = -3
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