<PRE><B>Question 872596</B>
Let p denote the event of success rate.
p=0.87

Using the Probability Binomial Distribution formula : 
P(X=r)= n C r (p) ^ r (1-p )^(n-r)


The probability that at least 10 will have positive result implies that either 10, or 11 or 12 people can have positive result. i.e we are required to find P(X=10) + P(x=11) + P(x=12)

Using the above formula.

12 C 10 * (0.87)^10*(0.13)^2      +      12 C 11 (0.87)^11 * (0.13)^1 +           12 C 12 (0.87)^12 *(0.13)^0

= 0.802</PRE>