If the two angles are complementary, it means the sum of their measures equals 90 degrees. The angles are given as (2x + 3)° and 2x°.
To express their relationship as an equation, we can set up the following equation:
\[ (2x + 3) + 2x = 90 \]
Combining like terms, we get:
\[ 4x + 3 = 90 \]
So the equation for the angle measures is:
\[ (2x + 3)° + 2x° = 90° \]