Not entirely sure, if this is the best place for this.
In the following news article first ‘quiz’ seems to have incorrect answer (or it has incorrect example).
y = 2x
y = 3(x + 1)
Does not expand to
2(2x) = 3(x + 1)
What further results propagates to different answer than it should and quiz not having the result matching example to solve.
https://www.freecodecamp.org/news/how-to-solve-a-system-of-linear-equations/