Solution
Step 1
Write an expression for the volume of a cuboid
[tex]\text{Volume of cuboid = L}ength\text{ }\times width\times height[/tex]Step 2
Find the volume of the first rectangular tank
[tex]\text{Volume of first tank =}18m\text{ }\times18m\times\frac{2}{3}\times6m=1296m^3\text{ }[/tex]Step 3
Find the volume of the second tank
[tex]\text{Volume of second tank = 12m }\times10m\times height[/tex]Step 4
Equate both volumes
[tex]\begin{gathered} 1296\text{ = 120}\times height \\ \text{height of water in second tank = }\frac{1296}{120}=10.8m \end{gathered}[/tex]Height of second rectangular tank = 10.8m
