Calculate the CoG

The center of gravity of a composite body is always the average of all its individual centers of mass, weighted by their respective masses.

${\mathrm{x}}_{\mathrm{S}}=\frac{\mathrm{\Sigma }({\mathrm{x}}_{\mathrm{i}}·{\mathrm{A}}_{\mathrm{i}})}{{\mathrm{A}}_{\mathrm{ges}}}$
and analog for y:
${\mathrm{y}}_{\mathrm{S}}=\frac{\mathrm{\Sigma }({\mathrm{y}}_{\mathrm{i}}·{\mathrm{A}}_{\mathrm{i}})}{{\mathrm{A}}_{\mathrm{ges}}}$

Cutouts are treated like regular bodies in the calculation. However, they act negatively, meaning their components are subtracted in the formula.

The centroid of a triangle is located one third of its length from the thick end. This applies to both sides, of course.