The water in this bottle is constant. Volume of water in the first bottle = bottom area x height of water = 10x4=40 cm2. There is as much water in the second bottle as in the first bottle. You can see that part of the second bottle has no water (rectangle). The volume of the blank plus the volume of water, that is, 40, equals the volume of the bottle. The area of the blank part is equal to (7-5) x 650.

Typing is very lucky, I hope it can be adopted. Thank you (actually, I just graduated from primary school). Hee hee.