Answer
$CO_{2}\\
C = 27.29\%\\
O = 72.71\%$
Work Step by Step
We can tell from the covalent name that the compound is a carbon atom bound to two oxygen atoms. Therefore the formula is $CO_{2}$. Adding up the molar masses of the constituent elements we get $44.01\frac{g}{mol}$ as the molar mass of the compound. So to find the percent composition we just multiply the molar mass of each element (found on the periodic table) by how many times it occurs, divide by the molar mass of the whole molecule and multiply by 100%. Here is carbon as an example:
$\frac{1(12.01\frac{g}{mol})}{44.01\frac{g}{mol}}×100\%=27.29\%$
