Respuesta :

let x = oxidation number of C 
Na has oxidation number = +1 
H has oxidation number = +1 
O has oxidation number -2 

+1 +1 +x + ( 3 x -2)=0 
1 + 1 + x - 6=0 
x - 4 = 0 

x = +4 

The answer is +4

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