Algebra-1

To solve the given system of equations using the elimination method, we can add the two equations to eliminate the variable "x". Let's perform the addition:

(x + 3y) + (-x - 4y) = 18 + (-25)

Simplifying the equation, we have:

x + (-x) + 3y + (-4y) = -7

The x terms cancel out (-x + x = 0), and the y terms combine:

3y - 4y = -y

Therefore, we have:

-y = -7

To solve for y, we multiply both sides of the equation by -1:

(-y) * (-1) = (-7) * (-1)