To find the value of \( a \) in a parallelogram, we typically use the property that opposite angles are equal. In this case, if you have two expressions for angles, we can set them equal to each other:
\[ 6a - 4 = 4a + 34 \]
Now, let's solve for \( a \):
- Subtract \( 4a \) from both sides:
\[ 6a - 4a - 4 = 34 \]
This simplifies to:
\[ 2a - 4 = 34 \]
- Next, add \( 4 \) to both sides:
\[ 2a = 34 + 4 \]
This simplifies to:
\[ 2a = 38 \]
- Finally, divide by \( 2 \):
\[ a = \frac{38}{2} = 19 \]
Thus, the value of \( a \) is:
\[ \boxed{19} \]