Some people may be able to figure it out in a few seconds, but we can use some variables to solve it. Let's call them "a" and "b".
We know that ab = -35, and a + b = -6
We can express one variable in terms of another, to reduce into a one-variable equation which is easy to solve!
We could write a = -6 -b, or b = -6 - a. Let's go with the first one.
(-6 - b)b = -35
-6b - b2 = -35
Wow, it's a quadratic (has an exponent of 2 on the variable) :D
We can rearrange this into the standard form for quadratic equations (ax2 + bx + c = 0).
-b2 - 6b + 35 = 0.
Using any method of solving quadratic equations, we get some really weird numbers for a and b that still fit:
\(-3 - 2\sqrt{11} \) and also \(2\sqrt{11} - 3\)
So, well... there's your answer! :D