Is the set (1,3,5,7) closed under subtraction?

Consider circle c with angle acb measuring 3/4 radians. if minor arc ab measures 9 inches, what is the length of the radius of circle c? if necessary, round your answer to the nearest inch.

Given: m zade = 60° and m2cdf = (3x + 15) prove: x = 15

F(x) = 2x + 1? h(x) = x – h(x) = x + h(x) = x – 2 h(x) = x + 2