So we know that angle LON is a straight angle. This means that angle LON is 180 degrees.
We are given that angle LOM is equal to 4x+30 degrees. So, we know that the sum of LOM+MON= 180 degrees:
Now, we can substitute this in the equation for MON!
8x+90= 8(5)+90=40+90=130 degrees
So sorry! I didn't realize these problems were already answered...
However, question 2 is a bit different than the link you are referring to, maybe it was a mistake?
Question 4's answer was incorrect. Other than those, your solution, and the one for question 3 were very helpful, thank you so much for those!