The equation \( 5x - 4y = 20 \) is a linear equation.
A linear equation is an equation of the form \( Ax + By = C \), where \( A \), \( B \), and \( C \) are constants, and the variables \( x \) and \( y \) are of the first degree (i.e., they are not raised to any power other than one and are not multiplied together).
In this case, \( A = 5 \), \( B = -4 \), and \( C = 20 \), which conforms to the standard form of a linear equation.