tolong nomer 18-19 ya

18.)L kubus
L = s x s
= 20 x 20
= 400
L lingkaran :
L = 1/4 x 22/7 x 10 x10
=78.5
L 1 - L 2 = 400 - 78.5 - 78.5
=243

19.) L= 3/4 x 22/7 x 28 x 28
= 1848