An element $X$ forms two oxides. Formula of the first oxide is ${XO}_2$. The first oxide contains $50\%$ of oxygen. If the second oxide contains $60\%$ oxygen, the formula of the second oxide is

Let the element be X

According to the first statement the oxide would be $X{O}_2$ as it contains 50%oxygen

Therefore, $\frac{32}{32+X}=0.5$

Thus the value of X = 32

According to the second statement, Let the molecular formula be $X{O}_n$

As the second oxide contains 60% oxygen so the relation would be as follows:

$\frac{16n}{32+16n}=0.6$

Therefore n=3

Thus the oxide is $X{O}_3$

Hence the correct option is (A).