You have to understand what makes an expression even. Even numbers are formed by either two odd numbers being added together or an even number x an odd number. We can start by looking at the denominator. Immediately we can see that 2x+9 cant be simplified into anything this is because there isnt a number that is a factor or 2 and 9. We can also see that the denominator has an x expression where as the top has x^2. Now down to the simplifying. We can see from the numerator that we can take out a factor of 4x as this goes into 8x^2 and 36x. Giving us 4x(2x+9). straightaway we can see that the number and denominator are the same. We can no cancel them out. leaving us with (8x^2 + 36x)/(2x + 9) = 4x4 is an even number and since any number multiplied by an even number is even. We have proven that the expression (8x^2 + 36x)/(2x + 9) is even