Determine wether the graph represents a proportional relationship. a) yes, its a proportional relationship because the graph goes through the origin. b) yes, its a proportional relationship because the graph is a straight line. c) no, it is not a proportional relationship because the graph is not a straight line d) no, its not a proportional relationship because the graph does not go through the origin.

we have three similar triangles, because each has a right angle and shares an angle.   let's write the angles in order: opposite to short leg, long leg, hypotenuse.

cab similar to bad similar to cbd

or as ratios,

ca: ab: cb = ba: ad: bd = cb: bd: cd

we also know

ac = ad + cd

(ad+cd): ab: cb = ba: ad: bd = cb: bd: cd

(ad+cd)/cb=cb/cd

we have cb=6, ad=5 and seek x=cd.

we reject the negative root and conclude x=4

answer: 4