The six marked angles are all the angles at the five vertices in the diagram, except for those that are the interior angles of the two triangles.

There are $360^\circ$ at each vertex he total of all the angles at the five vertices is $5 \times 360^\circ = 1800^\circ$.

There are two triangles, each of which has interior angles that add up to $180^\circ$. Therefore the total angle is $2 \times 180^\circ = 360^\circ$.

The marked angles are all the rest of the angles, so total $1800^\circ - 360^\circ = 1440^\circ$.