Verified Answer :

7 lbs 7 oz is a total of 119 oz
8 1/8 lbs is a total of 130 oz
So, the baby gained a total of 11 ounces.

so first:
7 ounces = 7/16   1/8 = 2/16 = 2 ounces
then:
8 pounds 2 ounces - 7 pounds 7 ounces = 11 ounces 
130 ounces - 119 ounces = 11 ounces
11 ounces is your answer