It stinks that Snape got fired from the Yow, but he needed to be at the garage anyway. Also he deserved it. Tobias is lucky Snape can make things happen otherwise nothing would get done. I loved Snape and Harry's time in the garage. Harry is going to be way more help than Tobias. 

I don't think Snape understands the point of word problems, lol. We (teachers) are trying to get students to identify relevant information and apply previously learned knowledge, which is more realistic than simply quizzing them with a list of facts. That said, some word problems are a bit silly. The one in Harry's homework is also poorly written. 

 I wonder if one day a muggle born student will pop in to the garage with their dad only to find that the mechanic is their old potions Professor. Imagine the shock- especially when Snape understands their father's Cumbrian and responds in kind.