Answer :
Given : The distance of mars is from the sun = 2.25 108 km
And
The distance of earth is from the sun = 1.5 108 km
So ,
The difference in the distance between the orbits of mars and earth = 2.25 108 - 1.5 108 = ( 2.25 - 1.5 ) 108 = 0.75 108 km ( Ans )