We are told the differentiable functions x and y are related by the following equation. Y is equal to square root of x. It's interesting, they're telling us that they're both differentiable functions. Even x is a function, must be a function of something else. Well, they tell us that the derivative of x with respect to t is 12. And they want us to find the derivative of y with respect to t when x is equal to nine. So let's just make sure we can understand this.