We are asked to find the solution to the given system of equations using the substitution method: $-x + 3y = -15$ (1) $7x - y = 25$ (2)

1. Problem Description

We are asked to find the solution to the given system of equations using the substitution method:

$-x + 3y = -15$ (1)

$7x - y = 25$ (2)

2. Solution Steps

First, solve equation (2) for y:

$7x - y = 25$

$y = 7x - 25$ (3)

Substitute expression (3) for $y$ into equation (1):

$-x + 3(7x - 25) = -15$

$-x + 21x - 75 = -15$

$20x = -15 + 75$

$20x = 60$

$x = \frac{60}{20}$

$x = 3$

Now substitute $x = 3$ into equation (3) to find the value of $y$:

$y = 7(3) - 25$

$y = 21 - 25$

$y = -4$

Therefore, the solution is $x = 3$ and $y = -4$.

3. Final Answer

The solution to the system of equations is $(3, -4)$.