I'm not really sure whether this is gamma distribution or not. But I found similar question in Gamma Distribution chapter. From my perspective, we need to find the lambda first, which I think it supposed to be 2/10 = 1/5 since it happens 2 per ten years. And I think we're asked to find the expectation but I'm not sure and I don't know how.
Suppose that, on the Richter scale, earthquakes of magnitude 5.5 or higher
have probability 0.01 of damaging certain types of brides. Suppose that such
intense earthquakes occur at a Poisson rate of 2 per ten years. How many years
is a bridge of this type expected to last in average?
So here I am guys. I hope you guys want to help me since I already give it all what I know. Thank you guys for your kindness.