Final answer:
Option A, ax - by=k, is an example of a literal equation as it contains multiple variables and expresses a relationship without solving for a specific value.
Step-by-step explanation:
A literal equation differs from other types of equations because it contains two or more variables and does not immediately solve for a specific value. Instead, it expresses a relationship between the variables. For instance, the formula for the perimeter of a rectangle P = 2l + 2w, where P stands for perimeter, l for length, and w for width, is a literal equation because it connects these three variables without providing a numerical answer.
Answering the specific question: Which of these is an example of a literal equation? Option A is the correct choice. The equation ax - by=k is a literal equation since it contains variables a, x, b, y, and k, and it relates these variables without solving for one specifically.
Options B and C are not literal equations because they are set equal to numerical values, indicating that they are standard linear equations meant to be solved for x. Option D is not an equation at all, as it lacks an equals sign and therefore does not express a relationship between x and y.