To determine when the two popcorn machines will have the same amount of popcorn left, we need to set up an equation based on the information provided.
Let's denote \( x \) as the number of hours since both machines started operating.
For Theatre A:
- Initial capacity: 100 gallons
- Rate of sale: 3 gallons per hour
- Amount left after \( x \) hours: \( 100 - 3x \)
For Theatre B:
- Initial capacity: 150 gallons
- Rate of sale: 5 gallons per hour
- Amount left after \( x \) hours: \( 150 - 5x \)
We need to set the two amounts equal to each other:
\[ 100 - 3x = 150 - 5x \]
This shows that after \( x \) hours, the amount of popcorn left in both machines will be the same.
So the correct equation is:
100 - 3x = 150 - 5x