The first thing you need to do is solve for *x*. You can do that by remembering that, when the probability of every possible outcome is summed, the total probability must sum to 100%. Do you see how you can solve for *x* with that information?
Once you have x, you'll know the probability of each individual outcome. From there you can simply add up the probabilities of getting an even number, which will allow you to calculate on average how many even numbers you expect out of 200 rolls.