I think it is they both have a 1 and a 0 in them.
Answer:
The answer is C, the third one.
You cant solve y but you can form an equation in terms of y
which is y=7-2x
if you were given another equation that has the term y and x than you can solve it.also that is a simultaneous equation.
Hope this helps,dont forget to put this as the brainliest answer if it does to help me out too. xD