Elizabeth is baking oatmeal cookies . a single batch used 3/4 teaspoons of vanilla. if elizabeth is mixing the ingredients for six batches at the same time , how many tablespoons of vanilla will she use?

So let's convert some stuff...
3/4 of teaspoon is equal to 0.75
Now since you want Elizabeth wants to make 6 batches of cookies you need to multiply 0.75 with 6 to get a number of teaspoons that need to be mixed.

So Elizabeth need 4.5 of vanilla teaspoons in her mix.