The volume of water from both cuboids equals the volume in the tank.<br><br>&bull; Volume of first cuboid = 24 × 10 × 9 = 2160 cm&sup3;<br>&bull; Volume of second cuboid = 18 × 12 × 5 = 1080 cm&sup3;<br>&bull; Total water = 2160 + 1080 = 3240 cm&sup3;<br><br>Tank volume = base area × height = 30 × w × 12 = 360w.<br>360w = 3240<br>w = 3240 ÷ 360 = 9 cm.<br><br>Final Answer: 9 cm