Pls help to solve this question, thank you!

First of all you count how many hours they together work a day.
20x8=160
They work 160 hours a day.
Then you need to find out how many hours they work during the whole building process.
160x54=8640
The building takes 8640 hours to build.
Then you need to find out how many hours it takes for 18 men to build this with just 7,5 hours a day.
7,5x18=135
To find out how many days it takes to build it:
8640/135=64
So it takes 64 days.
64-54=10
So it takes 10 more days.
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I hope that helps!
And sorry if it was confusing, english isn’t my first language...
20×8 equals 160 and then do 160×54 = 8640 and then do it again 7,5What times 18 equals 135 and then do 8640÷13 = 64 it takes 64 days 64-54 = 10 it will take you 10 more days longer hope this helps you and have a great day or a great night from where ever you are