We are given the mass of each reactant, so we can use the molar mass to find the number of moles.
Molar mass of $\mathrm{KO}_{2}$: $39.10 + 32.00 = 71.10 \ \mathrm{g/mol}$
Molar mass of $\mathrm{H}_{2}\mathrm{O}$: $2(1.01) + 16.00 = 18.02 \
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