If you guys don't help, then i migh have to cry. :( ( please help this is my test )

What is the measure of ac? 5 units 13 units 26 units 39 units 3x- 2b 6x + 9

Aword processing program requires a 7- digit registration code made up of the digits 1,2,4,5,6,7 and 9 each number has to be used and no number can be used mor than once how many codes are possible

*let m∠cob = 50°30’, m∠aob = 70° and m∠aoc = 20°30’. could point c be in the interior of ∠aob? why?