Answer:
In bold answers with correct units
3) 6 x 3 = 18 + 1/2 x 12 x 15 = 90 = 90+ 18 = 108ft^2
4) = 12 x 12 = 144 + 4x4 = 16 +12 x 4 = 48 = 144+12+48 = 204m^2
5) = 8 x 12 = 96 + 1/2 x 4 x 6 = 12 = 108ft^2
6) = 3x 3 = 9 + pi3^2 = 28.2743339 (x2) =56.5486678 + 9 = 65.5m^2
proves 4 semi circles = 2 circles
7) 10 x 8 = 80 +4 x 4 = 16 + 1/2 x 2 x 4 = 4 = 20+80= 100ft^2
proves 14-8-4 = 2ft is the triangle length and 10-6 = 4 the triangle height.
8) 4x6 = 24 + 1/2 x 4 x 2 = 4 + pi 4^2 = 1/2 x 50.2654825 = 24+4 + 25.1329 = 53.1m^2