"Laura, come on. It's not that hard," said Arnaldo, trying to be encouraging.

"But-I just don't get it! I did the thing, then the other thing, but I still don't get it! What now?! This makes no sense!" she exclaimed, putting her fists to her face and groaning.

"It makes perfect sense," said Arnaldo leaning over Laura's shoulder.

"You just have to put all the like terms together. See, here you have 3xy, 4x and 5xy. So what do you do there?"

Laura looked ...