To form the equation for the complementary angles, we start with the definition of complementary angles: two angles are complementary if their measures add up to \(90^\circ\).
Given the measures of the angles as \( (2x + 3)^\circ \) and \( 2x^\circ \), we can set up the equation:
\[ (2x + 3) + 2x = 90 \]
So, the equation representing the angle measures would be:
\[ (2x + 3)° + 2x° = 90° \]