Explanation:
You know that the three lines are parallel.
There weren't really any specific instructions so I'd assume that we're trying to find the lines. They are all in the same thing, as shown, one is 21 and the other is 12. That means the parallel line is cutting of 9.
We can then assume 2x+2-9=x+3
Then, to solve, you can get 2x-7=x+3
X=10
Hope this helped!
I'm a bit confused, but hope this helped again!