To find out how much farther Neptune is from Earth than Mars, we will first need the average distances of both planets from Earth:
- Average distance from Earth to Mars: Approximately 225 million kilometers (2.25 × 10^8 km).
- Average distance from Earth to Neptune: Approximately 4.3 billion kilometers (4.3 × 10^9 km).
Next, we calculate the difference in distance:
\[ \text{Distance from Neptune to Earth} - \text{Distance from Mars to Earth} = 4.3 \times 10^9 \text{ km} - 2.25 \times 10^8 \text{ km} \]
To perform this subtraction, we will first express both distances in the same power of ten. The distance to Mars can be written as:
\[ 2.25 \times 10^8 \text{ km} = 0.225 \times 10^9 \text{ km} \]
Now, we can perform the subtraction:
\[ 4.3 \times 10^9 \text{ km} - 0.225 \times 10^9 \text{ km} = (4.3 - 0.225) \times 10^9 \text{ km} = 4.075 \times 10^9 \text{ km} \]
Thus, the distance by which Neptune is farther from Earth than Mars is:
\[ \boxed{4.075 \times 10^9} \text{ km} \]