In the coding region, natural selection tends to eliminate all of the mutations because of the high importance these regions have. The coding region contains genes that synthesize proteins and the changes in the DNA sequence can have devastating effects on the cell. Therefore, there are very few differences in the sequences of coding regions that can help us trace the lineage.
On the other hand, in the non-coding regions, the mutations often accumulate because they have little effect on the cell and the adaptive value of the organism. This enables us to trace up the lineage by comparing the sequences and seeing the differences in the sequences.
To find an angle you use a variable like x or y. Sincw its a straight angle, it would be x +103 = 180. then you would subtract 103 on both sides. then you'll get x= 77 degrees
