What will the first step look like for the substitution problem:

[tex]\[
\begin{array}{l}
y = 2x \\
x + y = 9
\end{array}
\][/tex]

A. [tex]\( 2x + y = 9 \)[/tex]

B. [tex]\( y + 2x + x + y = 9 \)[/tex]

C. [tex]\( y = 2x + 9 \)[/tex]

D. [tex]\( x + 2x = 9 \)[/tex]