When superheated staemis passed through white hot charcoal, steam gets reduced to a mixture of X and Y.
`underset("White hot charcoal")(C ) + underset("Superheated staem ")(H_2O) underset("heat")overset("strong")toX + Y`

Explanation

X is CO , Y is `H_2`. The mixture of CO and `H_2` is called water gas.