Read this directions

a poor girl out with geometry lol the directions are: find the missing side. round to the nearest tenth. i know it has to do with tangents and stuff.
the directions for 136 is determine if line ab is tangent to the circle.
the directions for 138 is find the segment length indicated. assume that lines which appear to be tangent are tangent. the directions for 140 is solve for x. assume that lines which appear to be tangent are tangent