Question

1. \\(\

$$\begin{cases}x + 3y = -15 \\\\ y = -7\\end{cases}$$

\\)
solution:

Explanation:

Step1: Substitute \( y = -7 \) into the first equation

We have the system of equations \(

$$\begin{cases}x + 3y=-15\\y = -7\end{cases}$$

\). Substitute \( y=-7 \) into \( x + 3y=-15 \), we get \( x+3\times(-7)=-15 \).

Step2: Simplify and solve for \( x \)

Simplify the left - hand side of the equation: \( x-21=-15 \). Then, add 21 to both sides of the equation. According to the property of equality, if \( a - b=c \), then \( a=c + b \). So \( x=-15 + 21 \), and \( x = 6 \).

Answer:

The solution of the system of equations is \( x = 6,y=-7 \), that is \((6,-7)\)