Answer:
24 drops
Step-by-step explanation:
Well 2 half gallons is equivalent 1 one gallon
If the tub can hold 12 gallons, multiplying this by 2 to see how many half gallons this is would be: (12)(2) = 24 half gallons
If she needs 1 drop per every half gallon and the tub we now know can hold 24 half gallons, she must need 24 drops