Is 5.083 (the 3 is repeating) a rational number?

We just started the introduction into circles and i have no idea how to do this.

Suppose that the price p, in dollars, and the number of sales, x, of a certain item follow the equation 4 p plus 4 x plus 2 pxequals56. suppose also that p and x are both functions of time, measured in days. find the rate at which x is changing when xequals2, pequals6, and startfraction dp over dt endfraction equals1.5.

Which will form a composite function?