To find out when the two popcorn machines will have the same amount of popcorn left, we can set up the equations based on their capacities and selling rates.
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The amount of popcorn left in Movie Theatre A after x hours: \[ 120 - 7x \] (since it starts with 120 gallons and sells 7 gallons every hour)
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The amount of popcorn left in Movie Theatre B after x hours: \[ 150 - 9x \] (since it starts with 150 gallons and sells 9 gallons every hour)
Next, we can set these two equations equal to each other to find out when they have the same amount of popcorn left: \[ 120 - 7x = 150 - 9x \]
Now, let's solve for x.
First, we can add \(9x\) to both sides: \[ 120 - 7x + 9x = 150 \] \[ 120 + 2x = 150 \]
Next, subtract 120 from both sides: \[ 2x = 30 \]
Finally, divide both sides by 2: \[ x = 15 \]
Therefore, the two popcorn machines will have the same amount of popcorn left after 15 hours.
The correct option indicating this result is:
- \(120 - 7x = 150 - 9x ; x = 15\).