Answer:
50,803,200 ways
Step-by-step explanation:
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:

There are 50,803,200 ways to set the line-up.
It’s 1/4 because the first one is 1/4 and the second one is 2/8 which can be reduced to 1/4
To find the x-intersept, just set y = 0 into the equation, then solve it for x:
-2x + 5 * 0 = -10
-2x + 0 = -10
-2x = -10
x = (-10)/(-2)
x = 5 <----- this is the answer.
I hope this helps. =)