3x-4y=-24 X+y=-1 How Do I Do This Using Elimination?

Equation 1:
3x-4y=-24
Equation 2:
X+Y=-1
Equation 2 can also be written as:
X=-1-Y
Lets assume this is equation 3
SO:
Equation 3:
X=-1-Y
Substituting equation 3 into equation 1:
3(-1-y)-4y=-24
Expanding:
-3-3y-4y=-24
Subtracting:
-3-7y=-24
Shifting -3 to the other side:
-7y=-24+3
Subtracting:
-7y=-21
Dividing:
-y=-21/7
Which is:
-y=-3
Canceling the negative signs:
y=3
So y is 3
For X substitute this value of y into equation 3
Hence:
X=-1-Y
X=-1-3
Solving:
X=-4
So X is -4