Question

what is the first step when solving the system below by substitution?
x + y = 7
y = 2x - 1
substitute x in the second equation
substitute y from the second equation into the first equation
add the two equations together
multiply both equations by 2

Explanation:

To solve a system of equations by substitution, we need to substitute the expression for one variable from one equation into the other equation. Here, the second equation is \( y = 2x - 1 \), which gives \( y \) in terms of \( x \). So the first step is to substitute this expression for \( y \) into the first equation \( x + y = 7 \).

Answer:

Substitute \( y \) from the second equation into the first equation