Will give brainliest if correct

Given the two similar triangles, how do i find the missing length? if a=4, b=5, and b'=7.5 find a'

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.

What is the missing reason in the proof? segment addition congruent segments theorem transitive property of equality subtraction property of equality?