Mohon bantuannya kakk kakak..

L.permukaan balok = 2 (pl + pt + lt)
324 = 2 ( p x 5) + (p x 6) + (5 x 6)
324 = 2 (5p + 6p + 30)
324 = 2 ( 11p + 30)
324 = 22p + 60
324 – 60 = 22p
264 = 22p
264/22 = p
12 = panjang

jawabannya C. 12 cm

SEMOGA MEMBANTU YAA…