Well, we first know that Dominic uses 1/2 tablespoon. So if we use that 1/2 tablespoon on two sandwiches how many tablespoons does Dominic use? A whole! If you make another two sandwiches, then it will make another whole, and I whole plus one whole equals two wholes. Then, you make another one which uses another 1/2. And 1 whole plus one whole plus 1/2 a tablespoon equals 2 1/2!
