Half life of 15 over 8 Oxygen is 122 seconds.

How long does it take for the number of 15/8 O nuclei in a given sample to decrease by a factor of 1×10−4?
Answer in min.

I don't even know where to start. I have formulas but I don't know how to use them properly.
Any help is awesome!

I use the formula:

A_t = A_o \(\frac12\)^{t/h}

I can't see your factor clearly... :(

Anyway, from what is given, the half life is 122 s

The factor is given by At/Ao

So that you get:

Factor = \(\frac12\)^{t/h}

where h is the half life, t is the time in second you're looking for which you then need to convert into minutes, Factor is the factor given.

sorry factor did get all messed up... it was 1*10^-4
So I can do:
1*10^-4=(1/2)^t/h ?

I haven't done this in so long even my basic math sucks.. How can I get t by itself?

Okay, insert log

\log (factor) = \log \(\frac12\)^{t/h}

\log (factor) = \frac{t}{h} \log \(\frac12\)

\frac{\log (factor)}{\log \(\frac12\)} = \frac{t}{h}

t = h \frac{\log (factor)}{\log \(\frac12\)}