By substitution
4x + 8y = 20
-4x + 2y = -30

Step-by-step explanation:

In the picture, I hope that it's a clear solution and explanation.

(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

10 b/c 5*2 =10

step-by-step explanation: