A textbook costs $65.49 before tax. The tax on the textbook is 6.5%. What is the total cost of the textbook?

Round your answer to the nearest cent.

Enter your answer in the box.

Step-by-step explanation:

the tax will cost

65.49*6.5=4.26

the total price of the book is

65.49+4.26=69.75

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