3. On the line AB, point O is marked and from it rays OC, OD, OE, OF are drawn in the specified order into one half-plane of line AB (ray OC lies between rays OA and OD). Find the sum of all angles with vertex O, whose sides are rays OA, OC, OD, OE, OF, OB, if $\angle \mathrm{COF}=97^{\circ}, \angle \mathrm{DOE}=35^{\circ}$.
Answer: $1226^{\circ}$.

Instructions. There are four pairs of adjacent angles and a straight angle, which sum up to $180^{\circ}$ or are equal to $180^{\circ}$. There are two pairs of angles whose sum equals $\angle \mathrm{COF}$, and the angle itself. And there is still $\angle \mathrm{DOE}$. Therefore, the sum of the measures of all the required angles is

$5 \cdot 180^{\circ}+3 \cdot 97^{\circ}+1 \cdot 35^{\circ}=900^{\circ}+291^{\circ}+35^{\circ}=1226^{\circ}$.

Criteria. Correct answer without justification: 2 points.

For a computational error with correct reasoning, 3 points are deducted.