In the diagram, it looks like line segment AW is 6 units long and WB is 12 units long. Because of parts-whole postulate (the whole is equal to the sum of its parts), you can add AW and WB's lengths together. 6 + 12 = 18, so the length of line segment AB is 18 units long.
We can convert the values to percentage values and since a circle is 360°, we can multipy the percentages with 360° to get the degrees. The total of day is all the the things added up:
