It should be: triangle geometry * * * octagon, triangle triangle, geometric geometry

Triangle+geometry = 80 cents?

Triangle = triangular money, so geometry = fifty cents?

So: the answer is: fifty cents.

Next sentence? Bamboo is nine feet high, with the bottom folded to the ground, three feet away. How much does it cost to fold it?

?

Bamboo folds without folding. The top (the end refers to the treetop) touches the ground and forms a right triangle with the remaining stumps and the ground planted in the soil. The inclined part is the hypotenuse C, the lower section of bamboo stands upright as a right-angled side B, and the bamboo on the ground is another right-angled side A, where c+b=9 and a=3.

Pythagorean theorem c? -B? =3? =9，get (c+b)(c-b)=9，？ c-b=9/(c+b)=9/9= 1，

According to the simultaneous equations c+b=9 and c-b= 1, b=4 feet is the height of the upright bamboo pole.