Agree with E.
St1 : Distance between house and gas station could be anything. Insuff.
St2 : Gas station is 8 miles away from the house. Insuff.
Combine.
Distance between house and gas station is 8 miles. If the guy does not go to the gas station the distance is reduced by 4 miles.
house ---> 8 miles ---> gas station ---> x miles ---> store. Total = x+8.
house ---> y miles ---> store. Now, y = x+8-4 = x+4 (we dont know x.. right?).
Answer : E