Could someone solve for X, Y and Z

x=10,y=5,z=2

Step-by-step explanation:

x+15=2x+5

x=10

4y=8y-20

4y=20

y=5

10z-5=3z+9

7z=14

z=2

(n^3 - n)

= n(n-1)(n+1)

since it is divisible by 3 and 2 ,because it is a multiple 3 consecutive number

if, n-1 is odd then n+1 is also odd, then it is a multiple of 9

but if, n-1 is even then n+1 is also even, then it is a multiple of 4

so, largest multiple = max(9*2, 4*3) = max(18, 12) = 18

i believe the answer is the polygon, heptagon.