just do it this one i will mark you brainlist

Answer:
7 inches
Step-by-step explanation:
C = 31.4
Subtract 10.5
New circumference
C =31.4 -10.5
C =20.9
We know the formula for circumference is
C = pi *d
C = 3.14 * d
20.9 = 3.14 d
Divide each side by 3.14
20.9/3.14 =d
6.656050955
Approximately 7 inches