When using a 2/3 cup measuring cup it will take 1 and 1/2 of those 2/3 sized measuring cups to equal or make 1 cup.
So you'll need 1 of those 2/3 cups full and then the next cup that is 2/3 you would fill it halfway full to equal one cup.
An easier solution would be to get a measuring cup that measures in 1 cup so that you always get the correct amount of ingredients.
It takes two 1/4 cups to make 1 cup.
Well actually it takes a little over 2 of those 1/4 size cups to equal one cup.
So figure on 2 and 1/2 of those 1/4 cups to make 1 cup.
It takes 16 tablespoons to make 1 cup.
So if your recipe calls for 1 cup of ingredients then you need 16 tablespoons to equal the 1 cup of ingredients.
Or if you need to measure one cup of ingredients then take a tablespoon and then scoop up 16 of those tablespoons and then fill a cup or your bowl with it.
As long as you scoop up 16 tablespoons then you'll have 1 cup of ingredients.
So the short answer is that there are 16 tablespoons in one cup.
Having measuring cups as well as plenty of different sized measuring spoons can help really good in the kitchen.