A 85.2-mg sample of the compound X4O10 contains 48.0 mg of oxygen atoms. What is the atomic mass of element X?

Answer 1

85.2 - 48 = 37.2 mg of X

4 X atoms for every 10 O atoms

10 * 16 = 160

4 * X = 4x
4x/160 = 37.2/48

4 X = 160 *37.2/48

X = 31

check
31 * 4 = 124
16 *10 =160

124/160 = .775
and
37.2/48 = .775 good