The binomial probability of exactly x successes in n independent trials, when
the probability of exactly one success in one trial is p, is given by:



Here there are n trials so n = 4.  The probability of one success (cure) in 1
trial is .8, so p=.8

"More than two" means "three or four", and "or" means to add, so

the probability of 3 or 4 being cured is















.8192

You can also find that in the binomial table in your book
with n = 4 and p = .8

Or if you have a TI-83 or TI-84 calculator

On the calculator you have to consider the complement event as
1 - probability that 2 or fewer will be cured:
 
Press ON
Press CLEAR

Type 1-

Press 2ND
Press VARS
Press ALPHA
Press APPS

You should see this -->    1-binomcdf(   
followed by a blinking cursor.
After the parenthesis type this -->  4,.8,2)

You should see this -->    1-binomcdf(4,.8,
                           2)

Press ENTER

You should see the answer .8192

Edwin