It is common in mathematics to be given problems whose solutions involve more than one linear equation. Many situations involve information that can be presented in the form of two or more separate relations. In these cases, each relation may refer to the same unknown quantities. In the simplest of cases, we may see two equations, one of which is in the linear form: ax + by = c. While that equation by itself does not yield a unique solution, the second equation may reveal a value for one of the variables. Suppose, for example, that the second equation is in the form dx = e. From our earlier study, we know we can easily find the value for x here as x = e/d. Knowing this value for x will enable us to find the value of y in the first equation, as we shall shortly see.