One knief costs 5.52 dollars
Let the cost of knief be x dollars and the cost of spoon be y dollars.
A knife costs 3 times the cost of a spoon.
So, we get an equation,
x = 3y ..............(1)
9 spoons and 12 knives cost $82.80
So, we get an equation,
12x + 9y = 82.80 .........(2)
Substitute above value of x in equation (2),
12(3y) + 9y = 82.80
45y = 82.8
y = 1.84
Subatitute above value of y in equation (1),
x = 5.52
Therefore, the cost of knief is 5.52 dollars
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