Lines AB, CD and EF intersect at point O. Angle AOE-40 degrees; angle DOF-80 degrees. Find the COB angle measure.

In this task, we will find the degree measure of the angle at the intersection of straight lines;

To solve this problem, remember that the sum of all angles at the intersection of straight lines at one point is 360 °;

And the sum of the angles of a straight line is 180 °.

Adjacent angles at the intersection of straight lines are always the same;

Since all three straight lines AB, CD and EF intersect at one point, they form adjacent angles, which means that we will write down such equalities from the properties of these angles;

Angle AOE = BOF = 40 °;

Angle DOF = EOC = 80 °;

So the angle BOD = AOC = 80 – 40 = 40 °;

Then the COB angle = 180 – 40 = 140 °.