Hi there!
The answer is x = 6. All you have to do is subtract 83 from 127 because 127 is the total of the two parts of the equation. Now using the expression they give you - since you already know what the missing angle degree is for JKM- you just plug it in. 9x-10=44.
Add 10 to both sides to cancel out the ten.
You then have 9x = 54.
Divide both sides by 9.
Leaving you with x = 6.
Hope this helps !