How do you do this simultaneous equation?

The y is the same for both equations. Equate them
-x - 5 = 2x + 4 Add x to both sides
- 5 = 3x + 4 Subtract 4 from both sides.
- 9 = 3x Divide by 3
x = -9 / 3
x = - 3

y = - x - 5
y = -(-3) - 5
y = - 2

So that point is where the two equations meet.

To see the graph of your question on the internet, go to 
Wolframalpha.com 
and put this string in the question space.
y = -x - 5; y  = 2x + 4  Note the semi colon in the middle.

To the moderator: This is my own work. I'm using Wolfram to get the answer.

Photo math will give you the step by step answer : )