Let answers be x and y.

To add them, put a plus sign "+" between them,like this: x+y

"To get 6", you write "= 6" after it, like this:  x+y = 6

To multiply them, putting a multiplication symbol (dot) "∙" between them,like this:  x∙y

"To get -86", you write "= -86" after it:  x∙y = 6

x+y=6
x∙y=-86

To solve that you solve the first equation for one of the letters, say, y:

x+y=6
  y=6-x

Now you substitute (6-x) in parentheses for x in the other equation 

      x∙y=-86
  x∙(6-x)=-86
    6x-x²=-86

Get 0 on the right by adding 86 to both sides:

 6x-x²+86=0

Write the terms of the left side in descending order:

-x²+6x+86=0

We want the x² term to be positive so we multiply every term on
both sides by -1:

 x²-6x-86=0

That does not factor, so we use the quadratic formula:

 

a = 1, b =-6, c = -86

You finish:

Answer: , 

Edwin