A literal equation is an equation that involves multiple variables, often representing known values or constants. It is typically solved for one variable in terms of the others.
Given the options:
A. [tex]\(3x - 4y\)[/tex]: This is an algebraic expression, not an equation because it lacks an equality sign.
B. [tex]\(12 = 9 + 3x\)[/tex]: This equation involves numbers and only one variable, [tex]\(x\)[/tex], but it does not represent a general form that involves multiple variables.
C. [tex]\(6 + 30 = 6^2\)[/tex]: This is a numerical equation but does not involve variables.
D. [tex]\(ax - by = k\)[/tex]: This equation includes multiple variables ([tex]\(a\)[/tex], [tex]\(b\)[/tex], [tex]\(x\)[/tex], [tex]\(y\)[/tex]) and a constant [tex]\(k\)[/tex].
Option D, [tex]\(ax - by = k\)[/tex], is a typical example of a literal equation as it encompasses variables representing various unknowns and constants.
Hence, the correct choice is:
D. [tex]\(ax - by = k\)[/tex]
