Top 10.746

Radius R = 25 / 8 = 3.125

Orange Area = 32.3223304703

X = ABC = 100

Simplified

Another Elaborated Approach

Missing  Angle ABC = 60

Radius R₁ = 2

Elaborated

Green Area = 30

Pink / Yellow = 1. ADC = 30

Green Area = 5.48256055498

Missing Segment X = 3

Improved / Elaborated

X = Line Segment CM = 15

New / Improved / Simplified