Total angle of a polygon
= (Number of sides - 2) x 180°

So, for the pentagon,
Total angle = (5-2) x 180°
= 3 x 180°
= 540°

(Another way to see this is to cut the pentagon into 3 triangles. Each triangle has a angle sum of 180°. So 3 triangles give you 540°)

For the triangle below the pentagon, it is just 180°.

Notice that (each of the exterior angle) + (the interior angle they surround) = 360°. There are six of these 360°.

The exception is ∠g and ∠d.
∠g + ∠d + the two adjacent interior angles = 360°

So sum of all the interior angles of the polygons + angles a to h
= 6 x 360° + 360°
= 7 x 360°
= 2520°

Total sum of angles a to h

= 2520° - sum of all the interior angles
= 2520° - 540° - 180°
= 1800°