The rate of a first order reaction is $1.5 \times 10^{-2}$ mol L$^{-1}$ min$^{-1}$ at 0.5 M concentration of the reactant. The half life of the reaction is :-

For a first order reaction, rate $= k[A]$.
$k = \dfrac{\text{rate}}{[A]} = \dfrac{1.5 \times 10^{-2}}{0.5} = 3 \times 10^{-2}$ min$^{-1}$
Half life of a first order reaction: $t_{1/2} = \dfrac{0.693}{k}$
$t_{1/2} = \dfrac{0.693}{3 \times 10^{-2}} = 23.1$ min
So the half life of the reaction is 23.1 min.