ok, then i will not begin.

why don't you explain how it was done to ACTUALLY help the others?

OK.

Given question: The percentage of an element X equal to 77.4%, 63.2%,69.6%, and 72%. If the compund with 77.4% X is XO, what is X, and what are the other compounds?

I started 77.4% X is XO. If 77.4% is X then O is 22.6%. I used the ratio of X: O = 3.4 : 1. I know the MW of O is 16g; so, 16g * (3.4) = 54.9 g X

I looked at the periodic table for finding the element of X. That is Manganese, Mn.

For the 63.2% , If Mn is 63.2% then O is 36.8%. The calculation is basically same as above, using the ratio of Mn : O = 1.7 : 1

I know from previous information that MW of O has been increased; 2(16g O)* (1.7) (Mn/O)= 54.9g Mn ; MnO2.

Now you can try with other to get answer 69.6% and 72%.