The only assumption needed to solve the problem is that the bottom line is indeed straight. Generally it will never be assumed in these types of learning practices that a straight line is a lie, because at that point you can never do a single problem ever. However an undefined angle can be cheesed.

Though it still bugs me on a fundamental level they will cheese the angle to bait a person into a wrong answer, it can teach a valuable lesson about verifying information.

We can solve this issue of a straight line being guaranteed by doing this. This actually is probably a really good practice considering the exacting nature of certain disabilities such as ADHD and Autism. However if you live in the US you need to just accept things like this because we will NEVER fund public education properly let alone consider accessibility beyond things mandated by the ADA