trapesium A=24 cm T=20 cm L=620 CM2. BERAPA B TRAPESIUM?

        Luas = 1/2 x t x ( a + b )
   620 cm² = 1/2 x 20 cm x ( 24 cm + b )
   620 cm² = 10 cm ( 24 cm + b )
24 cm + b = 620 cm² : 10 cm
24 cm + b = 62 cm
              b = 62 cm - 24 cm
              b = 38 cm

Luas Trapesium
620 = 1/2 x (a + b) x 20
620 = 1/2 x (24 + b) x 20
620 = (12 + 1/2b) x 20
620 = 240 + 10b
620 - 240 = 10b
380 = 10b
B = 380/10
B = 38 Cm

Maaf kalau benar ya kak, soalnya dikelas memang saya gak terlalu cerdas.