Let X and Y have the joint probability distribution given by

p(x,y) = exp(-(x+y)) for x>0 and y>0

what is P(X+Y<3)?

i know that i would need to use double integrals for dx and dy but i do now know what i can put as the range of x and y such that the condition is fulfilled.

for what values of Y is the conditional density p(x l y) defined?

thanks!