To solve the given system of equations using the substitution method, the first step is to solve one of the equations for one of the variables. Let's analyze the given system:
[tex]\[
\left\{
\begin{array}{l}
x - y = -1 \\
2x - y = 3
\end{array}
\right.
\][/tex]
The first equation is:
[tex]\[ x - y = -1 \][/tex]
To solve the first equation for [tex]\( x \)[/tex], we need to isolate [tex]\( x \)[/tex]. So, we add [tex]\( y \)[/tex] to both sides of the first equation:
[tex]\[
x = y - 1
\][/tex]
This gives us an expression for [tex]\( x \)[/tex] in terms of [tex]\( y \)[/tex].
Therefore, the first step in solving this system of equations using substitution is:
Solve the first equation for [tex]\( x \)[/tex].