Question 1168491
the first is 0.95^15=0.4633 assuming independence.   

At least 13 means 13,14,15
13 surviving is 15C13*0.95^13*0.05^2=0.1348
14 is 15*0.95^14*0.05=0.3658
The total is 0.9639

or 1-binomcdf(15,0.95,12)=0.9638, the difference due to rounding.  The last is more accurate.