60% of a sum of money is $120.00. calculate 40% of tha same sum of money

If 60% is $120, then by diving both the percent and the balance by 3, we se that 20% is $40.

Now multiply the 20% and $40 by 2, and you see 40% is $80.

not only in mathematics, scientific proof also are required in the other field of science. also maths proofs are of particular structure, containing steps and logics. so proving is like doing science, it is science. that's why it is important to prove. 

an inaccurate proof leads to errors, or stating results that are not accurate.  which wil mess the probelm up you dont want this

you didn't give me the choices, so i will just give you the graph so you can look at your choices and choose the right one.