The Cellular Connection buys new model Z-Phones for $80 each and sells them for $200. What is the percent markup, n, for the model Z-Phone?

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

cross multiplying, we get :

⇒ (3) × (5) = (9) × (x)

⇒ 15 = 9x

answer: no

step-by-step explanation: because the big angle will spread away the 2 side that it is on and make the opposite side even longer.