Hi!
In one batch she uses 3/4 teaspoon of vanilla
therefore in 5 batch she uses 5*3/4=15/4 teaspoons of vanilla.
as it is given that 3 teaspoons=1 tablespoon
the amount of vanilla used for 5 batches =(15/4)/3=(15/4)*1/3=5/4==1.25 tablespoons.
All the best.
