Question 1118003
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This problem allows a mental solution.


If x is the smallest, then the largest is 4x,  and then the condition states that


x + 2(4x) = 18,   or  9x = 18  ====>  x = 2.


Then the smallest number is 2, the largest number is 4x = 4*2 = 8,


and the middle number is the difference 14 - (2+8) = 4.
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To solve it using matrix method is like shooting a cannon at sparrows.