The next number in the sequence is always found by subtracting the number before the previous number from the previous number. So you calculate the number in position 3 by subtracting the number in position 1 from the number in position 2.
Watch out, subtracting a negative number is the same as adding the number.
130 - 13 = 117
117 - 130 = -13
-13 - 117 = -130
-130 - -13 = -117
-117 - -130 = 13
13 - -117 = 130