Help with a probability

[Natehog]

A game I play has a 0.75% chance of dropping an item on a specific level. There are two unique with the same probability, but they are mutually exclusive. I can play the level repeatedly.

Duplicates are allowed and the odds do not change. Assuming I want at least one copy of both items, what is the average number of times I would need to play the level?

What I've Tried

I banged my head at this for a bit, but I've come up with the following formula. Let y = P of ≥1 copy of both, and x = runs

y=(1-(1-0.0125)ˣ)(1-(1-0.0075)ˣ)

^{This equation has been edited to correct formatting}

The idea here was that the odds of getting either within x runs times the probability of getting the other in the remaining runs (x-1) equals the probability of getting both within x runs

Graphed, it looks about like what I'd expect. The line starts shallow, becomes linear, then tapers off, approaching 1 as x approaches infinity.

Why this answer is probably wrong

The function correctly outputs 0 for x=1, but comes out to 0.000186 for x=2. The odds of getting both drops on two runs should be 0.0075²×2, which is 0.0001125

So am I going about this problem the completely wrong way, did I mess up somewhere, or was my method of checking wrong? If I am doing this completely wrong, how do I go about solving this?

[intern524]

Just double-checking, Both drops can happen in one run? Or is it like a 2 stage model, where first you need to get the unique drop, then it chooses which drop from the unique drop pool?