##4.2xx10^(-5)## light years

Light-years is not an adequate measure for distances inside the solar system. Symply a light-year is a humongously large measure of distance.

The distance between Earth and Mars is at the most 400 million km, and could be as small as 55 million km.

https://en.wikipedia.org/wiki/Mars

Even with the larger distance we would obtain:

##(400xx10^6 km )/(300000 km//s)~1333s ##, which is about 22 minutes. So Mars can be at the most 22 light-minutes from .

Neverthless, here is your answer:

Just divide the time in seconds light takes between Earth and Mars, by the number of seconds within one year:

##1333/(365.25xx24xx60xx60)=4.2xx10^(-5)## light years