I am hoping that the a in c = ad is supposed to be x.
The formula for circumference is c = pi * diameter with 3.14 substituting for pi.
Let’s plug in some values
172.7 = 3.14d
Divide
55 = d
The diameter should be 55 cm.
That would be 8 because the answer is 8.21 and you round down to 8
12:7
because you add 7 and 5 and then there is the 7 for the book weight
I need more information to answer your question
