A medium sized apple has 70 calories. This is 10 calories less than 1/4 of the calories in an old chocolate bar. We need to find out how many calories are in the bar? What could be a model for the first step?

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Define x:
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Let x be the calories of the old chocolate bar.
Apple = 1/4 x - 10        ←First Step : Define apple with reference to the choc

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Information Given:
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Apple = 70 Calories 

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Find x:
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1/4 x - 10 = 70              
1/4 x = 80
x   = 320 calories

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Answer: The old chocolate bar is 320 calories.
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