by pi. For example if the circumfrence is 12.56 you would divide 12.56 3.14159 to get 4, which is the diameter of the circle.use the diameter to find the radius by dividing the diameter. by 2. For example, if the diameter is 4 the radius would be 2.
216+7c=517; 43 copies .... of he made 216 a week from the newspaper and and made 7 dollars per copy sold of his book it should be 216+7c=517 then you subtract 216 from both sides of the equation so 7c=301 then divide 301 by 7 = 43
