tolong ya kak,pakek cara.makasih

0,9 m = 90 cm
6 dm = 60 cm

L dinding 1 /D1=60 × 80 × 2 = 9600
L dinding 2/D2=90 × 80 × 2 = 14400
L alas = 90 × 60 = 5400

L D1 + L D2 + L alas =29400 cm persegi

L ubin = 20× 10 = 200 cm persegi

banyak ubin yg diperlukan = 29400 ÷ 200 =147 (c)