Ug von u was at the wrong place at the wrong time

Successful implementation of a new system is based on three independent modules. module 1 works properly with probability 0.96. for modules 2 and 3, these probabilities equal 0.95 and 0.90. compute the probability that at least one of these three modules fails to work properly.

If 1/√5+1/√5+1=p+q√r , find the values of p, q and r

What is always true when two whole numbers are subtracted?