Answer:
10 pounds
Explanation:
If it were 20 percent more than last month, then it would be 120 percent of what he weighed last month. So, since it is 120 percent of last month, then it would have to be 0.1 pounds per percent and 12 is 120 percent of last month s then it would make it 100 percent of last month. If it is 0.1 pounds per percent, the baby would have weighed 10 pounds last month.