To find the value of \( d \), we need to know how \( 126^\circ \) and \( (9d)^\circ \) are related. Without more context, I will provide two common scenarios: if they are angles that sum to \( 180^\circ \) or if they form a linear pair.
Scenario 1: Angles sum to \( 180^\circ \)
If \( 126^\circ \) and \( (9d)^\circ \) are supplementary angles, then:
\[ 126^\circ + 9d = 180^\circ \]
To solve for \( d \):
- Subtract \( 126^\circ \) from both sides:
\[ 9d = 180^\circ - 126^\circ \] \[ 9d = 54^\circ \]
- Divide both sides by 9:
\[ d = \frac{54^\circ}{9} = 6^\circ \]
Scenario 2: Angles form a linear pair
If \( 126^\circ \) and \( (9d)^\circ \) are also supplementary angles, the answer will be the same.
Thus, unless given additional context, the value of \( d \) is:
\[ \boxed{6^\circ} \]