For a reaction $\mathrm{\Delta }H:(+3\mathrm{kJ})\cdot \mathrm{\Delta S}=(+10\mathrm{J}/\mathrm{K})$ beyond which

temperature this reaction will be spontaneous 

$\mathrm{\Delta }G=\mathrm{\Delta }H-T\mathrm{\Delta }S$ For the spontaneous reaction the $∆ G$ must be negative.  

$\begin{array}{r}\mathrm{\Delta }H=3\mathrm{KJ}=+3000\mathrm{J}\\ \mathrm{\Delta }S=+10\mathrm{J}/\mathrm{K}\\ \text{ If }T=300\mathrm{K}\Rightarrow \mathrm{\Delta }G=3000-300\times 10=0\\ \text{ If }T=200\mathrm{K}\Rightarrow \mathrm{\Delta }G=3000-200\times 10=1000\mathrm{J}\\ \text{ If }T=273\mathrm{K}\Rightarrow \mathrm{\Delta }G=3000-273\times 10=270\mathrm{J}\\ \text{ If }T=373\mathrm{K}\\ \mathrm{\Delta }G=3000-373\times 10=-730\mathrm{J}\end{array}$

Hence, beyond $373$ temperature the reaction will be spontaneous.