I'm thinking it may be b but i'm not too sure, can anyone out?

Try this solution:
C. 4<x<20.
explanation: according to rule: a+b>x,
where 'a' - the 1-st side 8 in., 'b' - the 2-d side, it is 12 in.

“exterior angles of triangles. an exterior (or external) angle is the angle between one side of a triangle and the extension of an adjacent side. try this drag the orange dots on any vertex to reshape the triangle.” look to get to the answer i explained what it means and other things i hope it you .

The linear equation is: y=ax+b