Final answer:
Eric needs to ride 8 more miles to complete his 20-mile journey, as he has already ridden 12 miles. The calculation is simply 20 miles minus 12 miles.
Step-by-step explanation:
The question asks how many more miles Eric needs to ride to complete a 20-mile trip if he has already ridden 12 miles. To find the remaining distance Eric needs to cover, we subtract the miles he has already ridden from the total distance of the trip.
Total distance to ride = 20 miles
Distance Eric has ridden = 12 miles
To find the remaining distance, we use the following subtraction:
20 miles - 12 miles = 8 miles
Therefore, Eric needs to ride 8 more miles to complete his 20-mile bike journey.