Answers

2015-06-24T00:47:35+08:00
It's really simple, as you can see,   *Summing Up* means sum (addition or add)
You just need to add it, Example No.1
25 + 20 + 10 + (-4) = 51
Example No.2
47 + 30 + 5 + (-11) = 71

You can do it alone, just sum it up and be careful to the numbers which has a negative sign or minus.
1 5 1
Ahhh.. so there's no thing such as Commond Difference? I just need to sum it up and that is it. Thanks!