Hello Girls and Guys I am really in bit of a pickle here as to how to do this mini maths problem which is due Monday. My teacher is hopeless as she just dumps the work without explanation on us. My girlfriends can hardly help as they have a high amateurishness threshold towards mathematics, as do I. Help would be appreciated. My contact email is lesbianista@hotmail.com. Oh and by the way we got this on Friday to do over the weekend.

Problem
An aeroplane has
crashed in the desert at
a point that could be
labelled (−15, 12) on a
particular grid system.
A search party sets out
by 4WD from the point
(18, 3) and travels in a
straight line passing
through the point (3, 9).
A light plane sets out
from point (3, −15) and
travels in a straight line
passing over the point
(−3, −6).

1. Will either of the search parties pass the point where the aeroplane lies if they continue
2. If either (or both) of the original routes does not pass the point where the aeroplane lies,
give a different point (but with the same x-coordinate) that the searchers should pass
through (or over) to be on course to locate the aeroplane.

How my teacher wants it set out

1) Draw a labelled Diagram of information given in 2-D with a labelled set of axis and points clearly labelled.
2) Use above diagram to write equation of line created by both search parties (with working)
3) Show algebraically whether each party will pass where the plane crashed.
4)If either or of both planes do not line on the correct path;
(a)Find a new point (but with the same x-coordinate) that the searches should pass over to be on course to find the aeroplane.
(b) Prove algebraically that this new route will find the aeroplane.

Thanks

Two questions:

a) Do you know how to find the equation of a line when you are given two points on the line?

b) Do you know how to determine if a particular point is on a line when you have the equation for the line?

If not, I will be glad to help, but I want to get a feel for where you are with this first.