Question

a system of equations is shown.\\(
\

$$\begin{cases} x + y = 3 \\\\ 3x - 4y = -5 \\end{cases}$$

\\)\
which is a correct step in solving this system of equations by substitution?\
\\(\bigcirc\\) substitute \\(x + 3\\) for \\(x\\) in the equation \\(3x - 4y = -5\\).\
\\(\bigcirc\\) substitute \\(x + 3\\) for \\(y\\) in the equation \\(3x - 4y = -5\\).\
\\(\bigcirc\\) substitute \\(-x + 3\\) for \\(x\\) in the equation \\(3x - 4y = -5\\).\
\\(\bigcirc\\) substitute \\(-x + 3\\) for \\(y\\) in the equation \\(3x - 4y = -5\\).

Explanation:

Step1: Isolate y from first equation

From $x + y = 3$, rearrange to get $y = -x + 3$.

Step2: Match substitution rule

Substitute the expression for $y$ into the second equation $3x - 4y = -5$.

Answer:

Substitute $-x + 3$ for $y$ in the equation $3x - 4y = -5$.