Ahayride costs $8 per person, and there is a 25% discount for children, students, and senior citizens. if there are (p) people who do not qualify for the discount and (s) people who do qualify, which equation can be used to calculate the revenue (r)? a r = 8p - 6s b r = 8p + (0.75)(8)(s) c r = 8p + 0.75s d r = 8p + (0.25)(8)(s)

the answer for this question is D

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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