In this situation, since you should alternate girl-boy or boy-girl, the line-up can either start with a boy or a girl kicking which would yield one of the two following patterns:
BGBGBGBGBGBGBG or GBGBGBGBGBGBGB.
For each of those patterns, there are 7! ways to arrange all boys and 7! ways to arrange all girls. The number of ways that a line-up can be made for one round of kicking is:
The absolute value of a number will never be negative because absolute value is the distance from zero, so it will always be positive. For example, you can't be -6 away from 0, you are 6 away from 0.
We don't know how many cars James has but we know they have 't'. But we know Paul has 13 cars. The question asks if Paul hands over half of his cars to James how many would James have? Well, 13 / 2 = 6.5
If James right now has 't' cars then after Pauls give his cars, then James will have t + 6.5.