The decomposition of N₂O₅ in carbon tetrachloride medium is given as $2{\mathrm{N}}_2{\mathrm{O}}_5⟶4{\mathrm{NO}}_2+{\mathrm{O}}_2$ . Then the rate is best related as

According to the reaction given in the question, the rate of the reaction can be written as:

$-\frac{1}{2}\frac{{\mathrm{\Delta N}}_2{\mathrm{O}}_5}{\mathrm{dt}}=\frac{1}{4}\frac{\mathrm{\Delta }{\mathrm{NO}}_2}{\mathrm{\Delta t}}=\frac{{\mathrm{\Delta O}}_2}{\mathrm{\Delta t}}$

So it can be written as:

 $\frac{{\mathrm{\Delta N}}_2{\mathrm{O}}_5}{\mathrm{dt}}=\frac{1}{2}\frac{\mathrm{\Delta }{\mathrm{NO}}_2}{\mathrm{\Delta t}}$