Find the number of tiles in the 57th figure

Another type of subtraction equation is 16-b=7. explain how you would sole this equation then solve it.

7+(3n++8) what is the answer to this?

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.