A real gas  behaves like ideal gas at temperature 

Vander waals equation can also be written as 

pV = nRT + np[b - $\frac{\mathrm{a}}{\mathrm{RT}}$]

Substituting T = $\frac{\mathrm{a}}{\mathrm{Rb}}$ in the above equation , it changes to pV = nRT.

Real gas obeys ideal gas equation

Note: T =$\frac{\mathrm{a}}{\mathrm{Rb}}$ is boyle temperature at which real gas behaves like ideal gas