Solve the system of equations

x-y + 9z = -27
2x – 4y - z= -1
3x + 6y - 3z = 27

Hi my sisters and brothers can tell me the answer because i don’t understand the question

Consider a cube that has sides of length l. now consider putting the largest sphere you can inside this cube without any point on the sphere lying outside of the cube. the volume ratio -volume of the sphere/ volume of the cube is 1. 5.2 × 10−1 2. 3.8 × 10−1 3. 1.9 4. 2.5 × 10−1 5. 3.8

Arational number that is equivalent to -20/4?