Tolong dibantu yaa.. Terima kasih​

Jawab:

AB + CD = 56 cm

Penjelasan dengan langkah-langkah:

    L = ¹/₂ (AB + CD) × t

420 = ¹/₂ ((3x + 3) + (x + 9)) × 15

420 = ¹/₂ (4x + 12) × 15

420 = (2x + 6) × 15

420 = 30x + 90

420 – 90 = 30x

330 = 30x

x = 11

AB + CD = (3x + 3) + (x + 9)

              = 4x + 12

              = 4(11) + 12

              = 44 + 12

              = 56

∴ AB + CD = 56 cm