Final answer:
The distance from the grocery store to the highway is 7 miles.
Step-by-step explanation:
To find the distance from the grocery store to the highway, we need to add the distances from the grocery store to the house and from the house to the highway. Therefore, the distance from the grocery store to the highway is 3 miles + 4 miles = 7 miles.
So, the correct answer is option b) 7 miles.