Answer: 19.5 cm
==========================================================
Step-by-step explanation:
The volume of a rectangular block is V = L*W*H. So we multiply the length L, width W and H.
For the smaller rectangular block, up to the water level shown, we have a volume of V = L*W*H = 12*8*7 = 672 cubic cm
Since 1000 cm^3 represents 1 liter, this means the tank has 672/1000 = 0.672 liters of water already.
Add on another 1.2 liters of water to get to 1.2+0.672 = 1.872
Therefore, the full tank's capacity is 1.872 liters
This converts to 1.872*1000 = 1872 cm^3
--------------------------------------------
The largest rectangular block has volume 1872 cm^3
We know the length and width (along the bottom) is L = 12 and W = 8 respectively. The height is unknown, but we can solve for it like so
V = L*W*H
L*W*H = V
12*8*H = 1872
96H = 1872
H = 1872/96
H = 19.5
The height of the tank is 19.5 cm