Please explain in detail how to solve this problem. The solution posted on Chegg is incomprehensible. Thank you.

Updte: Apparently Chegg doesn't allow copy$-$and$-$paste! So I$\text{'}$m including a screenshot of the question I need help with.At a particular temperature, $N_2{O}_5$ decomposes according to a first$-$order rate law with a

half$-$life of $3\mathrm{.}0s.$ If the initial concentration of $N_2{O}_5$ is $1\mathrm{.}0{10}^{16}$ molecules $\frac{?}{c{m}^3},$ what will be

the concentration in molecules $\frac{?}{c{m}^3}$ after $10\mathrm{.}0s??$