Chapter 1 - Equations and Inequalities - 1.8 Absolute Value Equations and Inequalities - 1.8 Exercises - Page 167: 25

The equation cannot have a positive solution because this will make the absolute value expression be equal to a negative number and this will never be true.

$|7x+3|=-5x$ A positive value of $x$ will make the right side of the equation negative. This means the equation will never be true because an absolute value expression will never produce a negative number.