Let's solve the equations step by step.
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For the first equation:
\[ 5x + 9 - 4x = 17 \]
Combine like terms:
\[ (5x - 4x) + 9 = 17 \]
This simplifies to:
\[ x + 9 = 17 \]
Now, subtract 9 from both sides:
\[ x = 17 - 9 \]
Thus, we find:
\[ x = 8 \]
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For the second equation:
\[ [?]x - 8 = 8 \]
We know from the first equation that \( x = 8 \). To fill in the blank, we substitute \( x = 8 \):
Rewriting the equation:
\[ k \cdot 8 - 8 = 8 \]
Now, add 8 to both sides:
\[ k \cdot 8 = 16 \]
Divide both sides by 8:
\[ k = 2 \]
So, the answers are:
- From the first equation, \( x = 8 \).
- From the second equation, the missing coefficient is \( 2 \).
Thus, the filled answers are:
- \( x = 8 \)
- The coefficient is \( 2 \).