Simplify the following expression:
-2r(3r - 5) + 0.75r - r²

A. -r² - 5.25r + 10
B. -7r² + 10.75r
C. -5r² + 0.75r + 10
D. The expression is fully simplified.

The pyraminx is a rubik's cube-type toy in the shape of a tetrahedron. the pyraminx shown below has edges 15\,\text{cm}15cm long and vertical height h=12.2\,\text{cm}h=12.2cm. the triangle drawn with dashed lines is a right triangle. what is the distance rr? round your answer to the nearest tenth.