X=12 you take away 1x from four then divide 36 by 3x
Replace the x with 9, and the y with 1.
(x · y²)/-5 becomes (9 · 1²)/-5
1² is just 1, so you're doing 9 × 1 (which is = 9) over -5.
Therefore, your final answer is -9/5.
The answer is the option A, which is: A. Equilateral triangles.
The explanation for this answer is shown below:
By definition, a tetrahedron is a solid in three dimensions that has: six sides, four vertices and four triangular faces. These faces are equilateral triangles, which means that all the sides are equal and all the interior angles measure
degrees.
The tetrahedron is also called "triangular pyramid".