Pls. see attachment. I created that table for easy monitoring and understanding.
Yellow cells are sums that are even.
Orange cell are sums that are multiples of 3.
Yellow cells w/ orange texts are sums that are both even and multiples of 3.
B and c are the factors because they make the product
Distance from home to store = 4 * 0.5 = 2 miles.
Time taken to return home = (2/12) * 60 =10 minutes.
Total distance traveled = 2 * 2 = 4 miles.
Total time taken = 30 + 10 = 40 minutes.
Average speed for entire trip = total distance / total time in hours.