step by step explanation:
the angles on the inside of the pentagon=
\(180\times(5-2)=540\)
the angles on the inside of the trapezoid =
\(180\times(4-2)=360\)
7x360-360-540=
5x360-180=
1800-180=1620.
But we counted F and C as 360 + F and 360+c, so
1620-720=\(\boxed{900}\)