We can solve this because of several different laws of lines and angles. We know that 4x+35+5x-8 has to equal 180 because of these laws. Now that we have a value to set it equal to, we can solve.
4x+35+5x-8=180
9x+27=180
-27 -27
9x=153
/9 /9
x=17
Now we have a value for x, which means we can substitute 17 in for anyplace we see an x.
5x-8
5*17-8=77
4x+35
4*17+35=103
If you would like to check your answer, you can add 77 and 103 together which will equal 180. If it did not equal 180, you would know it is incorrect.
Therefore, we know that x=17, the angle on line m=77, and the angle marked on line n=103.