this would be because the 20 is 19.8 tons rounded up, the (1.1) is the increase of the original amount plus the 9.8 rounded up, and the (1.05) is the increase by 5.1. the reason why they multiply these like 20(1.1)(1.05) is because each number in the parenthesis is the increase, when you multiply something by 1.1 it will give you it's 100% + the 10% growth, same goes for the 1.05 which will give you the 100% + the 5% of 20(1.1)
in other words if you just multiplied by .1 you would only get 10% of what you're seeking while if you multiply by 1.1 you would get the 110%. the 1 is 100%, and the extra percentage you seek is the decimal (number behind the dot) that follows
