Expected value from points in triangle

[Messagehelp]

I've been trying to figure out this problem in a book of mine. Done lots of reading but lost as to what I should be doing.

A point is chosen at random from a triangle with corners at (0, 0), (2, 0) & (1, 1). Let (X, Y) be the coordinates of the point chosen.
a) Find the joint pdf of X, Y
b) Calculate the marginal pdf's of X and Y .
c) Find the mean and variance of X.

I understand how to find joint pdf, marginals, mean and variance from an equation but I'm unsure how to start.

 

[royhaas]

The joint density is uniform over the isosceles triangle, which has area 1. That's the only reasonable interpretation of "choose a point at random in the triangle".