To arrive at Line 1 from the original equation \( x + 2(x + 1) = 17 \), the student combined the terms \( 2(x + 1) \) which involves distributing the \( 2 \) to both \( x \) and \( 1 \).
The proper way to describe this operation is:
- The student expanded \( 2(x + 1) \) using the Distributive Property, which gives \( 2 \cdot x + 2 \cdot 1 = 2x + 2 \).
Thus, combining this with \( x \) gives \( x + 2x + 2 \).
Therefore, the correct answer is:
C) Distributive Property.