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Math·Algebra·Linear equations in one variable

hard

Each side of a 30-sided polygon has one of three lengths. The number of sides with length 8 cm is 5 times the number of sides with length 3 cm. There are 6 sides with the third length. If $n$ is the number of sides with length 3 cm, which equation must be true for the value of $n$?

A

$5n+6=30$

B

$6n+6=30$

C

$4n+8n+3n=30$

D

$4(5n)+8n+3(6)=30$