Answer:
To find how much yarn Tina used for the third doll, we can subtract the total amount of yarn used for the first two dolls from the total amount of yarn used.
Total amount of yarn used = 10 1/2 yards
Amount used for first doll = 3 1/2 yards
Amount used for second doll = 4 1/8 yards
To add 3 1/2 and 4 1/8, we need to find a common denominator:
3 1/2 = 7/2
4 1/8 = 33/8
Common denominator = 8
So, 3 1/2 = 28/8 and 4 1/8 = 33/8
Total amount used for first two dolls = 28/8 + 33/8 = 61/8
Subtracting the total amount used for the first two dolls from the total amount of yarn used:
10 1/2 - 61/8 = 84/8 - 61/8 = 23/8
Therefore, Tina used 23/8 yards of yarn for the third doll.