Step-by-step explanation:
the formula to calculate a circumference is

(consider x as the diameter)
so I'll be noting the circumference as C alongside the circle's ranking
a.

b.

c.

hope I helped
Answer:
the answer is 2100
Step-by-step explanation:
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18% because take the first digits of each number and put them together lol
4+3(7+4 x 2)-100
4+3(7+8)-100
4+3(15)-100
4+45-100=
-51