Movie Theatre A has a popcorn machine with a 100-gallon capacity, and sells 3 gallons of popcorn per hour.

Move Theatre B has a popcorn machine with a 150-gallon capacity, and sells 5 gallons of popcorn per hour.
Write an equation to show when the two popcorn machines will have the same amount of popcorn left. Use x as your variable.
a 100 + 3x = 150 + 5x
b 150 + 3x = 100 + 5x
c 100 - 3x = 150 - 5x
d 3x - 100 = 5x - 150