Now that I think about it more, I think this is an inverse norm problem. I think I need to say the mean is .15 the SD = .0462 and then the invNorm of it being less than 90% would be 25.92%
1. I first started by finding the Standard Deviation and got it to be SD = sqrt((.15)(.85)/75) = .0412
2. I then thought it was was a probability they wanted me to find and deal with a normal distribution.
I found the normalcdf (-1000000000,.9,.15..0412) and I got 1. I assumed that was wrong...