If x is an even number, what is the difference between the smallest even number greater than (5x + 6) and the largest even number less than (3x + 9)?

Given that,
x is even

Now,
5x + 6 = odd×even + even = even + even = Even number.
So, the smallest even number greater than (5x+6) is = (5x+6) + 2 = 5x+8

And,
3x+9 = odd×even + odd = even + odd = Odd number,
So, the largest even number less than (3x+9) is = (3x+9) – 1 = 3x+8

So, the difference = (5x+8) – (3x+8) = 2x