Solve the system by substitution.
1. y = -6x – 7
y = -7x

2. -y=x
3x+5y=20

For no. 1:

One of the equations say that y=-7x

So plug in -7x to the other equation as y so you equation would be

-7x= -6x-7

And then, just solve for the variable:

*add -6x to both sides*:

-x= -7

*multiply both by negative one to get a positive variable*

FOR NUMBER 1, THE ANSWER IS:

x=7

Y=-7

For no. 2:

-y=x and your other equation is 3x+5y=20

Plug in x as -y:

-3y+5y=20

*simplify*

2y=20

*divide by 2 on each side to get 1 variable alone*

Y=10

FOR NUMBER 2, THE ANSWER IS:

x=-y

Y=10