Tank A measuring 40 cm by 20 cm by 80 cm,is filled with water to the brim.Tank B is an empty rectangular container with a base area of 60 cm

Tank A measuring 40 cm by 20 cm by 80 cm,is filled with water to the brim.Tank B is an empty rectangular container with a base area of 60 cm by 40 cm.What is the volume of water that must be poured into Tank B from Tank A such that they have the same height in the end?

$$\\20cm*40cm*(80cm-h)=40cm*60cm*h\\
20cm*(80cm-h)=60cm*h \quad | \quad :20cm\\
80cm-h=3h\\
4h=80cm\\
\boxed{h=20cm}$$

What is the volume of water that must be poured into Tank B from Tank A such that they have the same height in the end?

$$\textcolor[rgb]{1,0,0}{V=}40cm*60cm*h=40*60*20\;cm^3=\textcolor[rgb]{1,0,0}{48000\;cm^3}$$

So, assuming that 80 cm is the height of the first tank, the volume of water in the first tank =

40*20*80 = 64000cm^3

Note that the volume of water remains constant and is divided between the two tanks thusly:

40*20*h + 60*40*h = 64000   

800h + 2400h = 64000

3200h = 64000

 h = 20

So, both tanks would be filled to a height of 20cm

And the volume of water that would be poured from Tank A = 40*20*(80-20) =

48000cm^3