Subtract 5 from both sides to get 3x = 15, then divide by 3 to find x = 5.

5 divides 30 evenly, so it is a factor.

11 has no divisors other than 1 and itself.

Solving for x gives 2x = 8, so x = 4.

If n = 2k, then n^2 = (2k)^2 = 4k^2, which is even.

Distributing gives 6x + 12.

18 is divisible by both 2 and 3, hence by 6.

Combine like terms: 2x + 3x = 5x, so the polynomial is 5x - 4.

Combine like terms: (2x^2 + 4x^2) + (3x - x) - 5 = 6x^2 + 2x - 5.