Good point.
No I did not. I’ll try that now.
The problem tells us three things:
I. The three lines intersecting at O - \overline {BE}, \overline {CF} & \overline {AD} - are straight lines
II. ∠COD = ∠DOE
III. Ratio of ∠COB to ∠BOF is 7:2
Ok I see the issue…
Somehow I skipped over II and didn’t use that.
Based on the information in the problem, we can deduce that ∠COB = 140° and ∠BOF = 40°. ∠BOF is a vertical angle to ∠COE, so ∠COE is also 40°. ∠COE is composed of two angles, ∠COD and ∠DOE, which are equal to each other, and so the 40° of ∠COE must be equally divided amongst these two angles. So I think that ∠COD = 20°.
As a methodology improvement, I think I should try writing out the information that is given by the problem, without doing any deductions from that information, in a separate section of my answers, so that I make sure I’ve got it straight what information I have and what information I’m adding.