At 7 weeks old, the puppy weighed 6 pounds, but doubled in weight by week 9 to reach a weight of 6*2=<<6+6=12>>12 pounds.
It doubled in weight again at 3 months old to reach a weight of 12*2=<<12*2=24>>24 pounds.
It doubled in weight again at 5 months old to reach a weight of 24*2=<<24*2=48>>48 pounds.
And it reached its full adult weight by adding another 30 lbs to reach a final weight of 48+30=78 pounds.
#### 78