Thread: Conditional probablity mass function problem -- need help please!

Suppose that the random variables X and T have the joint probability mass function

p(x,t) = P(X=x, T=t) = p^2(1 − p)^t-2, t = x+1, x+2,···, x = 1,···,t − 1,
where 0 < p < 1.

Find the marginal probability mass function of T.


I really have no clue how to do this question

to get the marginal of T, you need to sum over x.

I started working on this and I have a feeling the distribution is incorrect.
Don't you need an x somewhere in this???