Answer:
23.5 - 18.7 = x
Step-by-step explanation:
Isolate the variable
M, or slope, is needed to define if a set of lines are parallel or not.
See attachment for math work and answer.
(I'm not totally sure but there may be someone else with a more accurate/correct answer.)
Here is what I got (Red represents my work, blue represents to follow which steps and highlighter represents what the answer is):