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1. a) 130: 31+32+33+34
b) -38: -8+(-9)+(-10)+(-11)

2. 5,6,7,8, because 5+6+7= 18, which is 10 more than 8

3. (a+d)-(b+c)=0
Explanation:
a+d and b+c equal the same solution, so when subtracted by each other, they will always equal 0.
Example:
(1+4)-(2+3)=0

4. 10+11+12-13= 20
11+12+13-14= 22
The answer is always double the lowest number in the sequence and is always even since it is divisible by two.