How do you add and subtract positive and negative numbers?

Positive + Positive = x + x
EX: 2 + 2 = 4

Positive + Negative = x - x
EX: -2 + 2 = 2 - 2 = 0

Positive - Negative = x + x
EX: 2 - (-2) = 2 + 2 = 4

Negative - Postive = -x + -x
EX: -2 - 2 = -2 - (-2) = -4

Negative + Negative = -x + -x
EX: -2 + -2 = -4

Negative - Negative = -x + x = x - x
EX: -2 - (-2) = -2 + 2 = 2 - 2 = 0

Basic rules to follow:
*A negative and a minus sign next to each other make it positive/addition
*adding a negative to a positive is the same as subtraction
*It's easier to see if you write equation with positive integer first, then negative
*Two negatives added together is still negative -- vice versa for positive
*A larger negative integer + or - a positive integer makes the answer more negative -- vice versa for positive integers

Skew lines(segments) are lines(segments) in 3 dimensions that do not intersect the given segment and are not parallel to it.  ae, bf, eg, and fh are your skew segments.  i hope that : )