Well the long way would be to solve algebraicaly two equations with two unknowns like this:

x+y=-12

x*y=36

solve the first eq for x:

x=-12-y

now sub it into eq 2

(-12-y)(y)=36

-12y-y^2=36

-y^2-12y-36=0

y^2+12y+36=0

(y+6)(y+6)=0

y=-6

now sub into either eq and solve for x

The short way to do it is just by looking at it.

1. -6,-6

2. -7,-5

4. -8,-4

5. -11,-1

6. -12,0