Need some clarification of how to add these probabilities.

Question

From a moment generating function I deduced that $P(X=0) = 0.4$, $P(X=1) = 0.3$ and $P(X=3)=0.3$. I am asked to find $P(X>0)$.

That would be:

$$P(X>0) = 0.3+0.3$$

right?

Answer 1

I think you made a typo. I think you meant to write $.3+.3 = .6$, which I think is right.

The way I see it is $$P(X>0) = 1-P(X\leq 0) = 1-.4 = .6$$ Assumming the smallest possible value is $0$. So I agree.