Question 68579
 P=12 units:Bottom (x-1),side 5,side x 
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I understand this to mean the perimeter of a triangle, with the given sides = 12
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The perimeter is the sum of all 3 sides:
(x-1) + 5 + x = 12
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Add the x's, 
x + x - 1 + 5 = 12
:
2x + 4 = 12
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Subtract 4 from both sides:
2x = 12 - 4
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2x = 8
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Divide both sides by 2 and you have:
x = 8/2
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x = 4
:
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Check our solution, substitute 4 for x: (4-1) + 5 + 4 = 12