A linear equation in one variable is an equation that can be written in the form ax plus b equals c, where x is the variable we want to find, a is the coefficient of x, and b and c are constants. For example, in the equation 2x plus 3 equals 7, the coefficient is 2, x is our variable, and 3 and 7 are constants. The solution is the value of x that makes the equation true, which in this case is x equals 2.