Y=x+5 and y=-2x-4 in substitution method

The two equations that have already been given in the question are
y = x + 5
And
y = -2x - 4
Now let us substitute the value of y from the first equation to the second equation, we get
y = - 2x - 4
x + 5 = - 2x - 4
x + 2x = - 4 - 5
3x = - 9
x = - (9/3)
   = - 3
Putting the value of x in the first equation, we get
y = x + 5
   = - 3 + 5
   = 2

Hi

y = x+5
y = -2x-4

x+5 = -2x-4
x+2x = -4-5
3x = -9
x = -9/3
x = -3

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

x = -3 and y = 2

Cd is the perpendicular bisector of both xy and st, and cy=20.find xy