A man owns a store. One week he sells 100 loaves of bread. If he sells twice as many loaves the next week, how many loaves did he sell in total?

First, calculate how many loaves of bread the man sold during the second week: $3990_w108_h13.png$
Then, add the number of loaves sold during the first week (100) to the number sold during the second week (200): 100 + 200 = 300