SOLUTION: Two sides of a triangle have lengths of 5 feet and 7 feet. If the triangle’s perimeter is 21 feet, what is the length of the third side?

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Question 757868: Two sides of a triangle have lengths of 5 feet and 7 feet. If the triangle’s perimeter is 21 feet, what is the length of the third side?
Answer by tasmart(9) About Me  (Show Source):
You can put this solution on YOUR website!
P=A+B+C
21=5+7+x
21-5-7=x
9=x
21=5+7+9