7 years
First of all, half of 18 is 9, and if you divide 18 by 2.5, it results in 7.2. I hope this helps!
Answer:
The amount of water left in the tank is approximately 58.1 cubic meters
Step-by-step explanation:
step 1
Find the volume of the a cube shape tank
The volume is equal to

we have

substitute

step 2
Find the volume of cone
The volume is equal to

we have



substitute


step 3
Find the difference of the volumes


Answer : He spends 2 hours doing paperwork each day.
Hope this helps. - M