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!
-24
-66+42
=-24 since it is negative
18, you have 3 choices for the bottom because you can't use the small one, 3 choices for the next because you can now use the small one, 2 for the next and finally 1. You multiply all of them to get 18
Simplify them until they can be simplified no more, then compare both sides.
