We can actually just do it directly. The expected value of y, let me just write it over here. The expected value of y is just the probability weighted outcomes, and since there's only two discrete outcomes here, it's pretty easy to calculate. We have a probability of p of getting a one, so it's p times one, plus we have a probability of one minus p of getting a zero. Well, what does this simplify to? Well, zero times anything, that's zero, and then you have one times p. This is just equal to p. So, expected value of y is just equal to p, and so there you have it. We get the expected value of x is 10 times the expected value, or the expected value of x is n times the expected value of y, and the expected value of y is p, so the expected value of x is equal to np.