Question 987420
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I am adjusting DC to be AC. If this is not correct, re-post your problem.
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AC=AC
AB=0.7AC
BC=0.7AC+3cm
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Perimeter=AB+BC+AC
Perimeter=0.7AC+(0.7AC+3cm)+AC
Perimeter=2.4AC+3cm
55cm=2.4AC+3cm
52cm=2.4AC
21.67cm=AC 
ANSWER 1:AC=21.67 cm
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AB=0.7AC=(0.7)(21.67)=15.17cm
ANSWER 2: AB=15.17cm
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BC=0.7AC+3cm=15.17cm+3cm=18.17cm
ANSWER 3: BC=18.17cm
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CHECK:
Perimeter=55cm
AB+BC+AC=55cm
15.17cm+18.17cm+21.67cm=55cm
55.01cm=55cm