To determine the equation for the angle measures, we can use the information given about the angles formed at point B.
We know that the angles A B C, A B D, and D B C add up to 90 degrees, since they form a right angle at point B.
Given the measures:
- Angle A B D = 4x degrees
- Angle D B C = (7x - 9) degrees
The equation that shows the sum of angles A B D and D B C equals the total angle A B C (which is 90 degrees) can be set up as follows:
\[ 4x + (7x - 9) = 90 \]
Therefore, the specific equation for determining the angle measures is:
(7x - 9)° + 4x° = 90°.