The length of the three pieces of a beam is required.
The length of one piece is 3 feet the other piece is 9 feet and the last piece is also 9 feet.
The length of the beam is 21 foot.
The length of the shortest beam is [tex]x[/tex]
Length of the second piece is 3 times the first piece, i.e., [tex]3x[/tex]
The same goes for the third piece [tex]3x[/tex]
[tex]x+3x+3x=21\\\Rightarrow 7x=21\\\Rightarrow x=\dfrac{21}{7}\\\Rightarrow x=3[/tex]
The length of the other two pieces is [tex]3x=3\times3=9[/tex]
The length of the shortest piece is 3 feet.
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