What is the sum of the first 6 terms of this geometric system
-5,10,-20,

Each one is multiplied by -2...

PROOF
-5 * 10 = -20
-20 * -2 = 40
And so on.

So we need two more numbers so do 40 * -2...

40 * -2 = -80

And then...
-80 * -2 = 160

So the first 6 numbers are...
-5, 10, -20, 40, -80, 160.

We need to find the SUM, which is all the numbers added together.

-5 + 10 - 20 + 40 - 80 + 160 = 105

105 is your answer.