Check the picture below.
so, that'd be 20.24845673131658693325, and to the nearest tenth it'd then be 20.2
80% of 20 is 80/100 x 20 = 16
So, kelly has used 16 stamps, and has 4 left
We have given the table of number of male and female contestants who did and did not win prize
The probability that a randomly selected contestant won prize given that contestant was female is
P(contestant won prize / Contestant was female)
Here we will use conditional probability formula
P(A/B) = 
Let Event A = selected contestant won prize and
event B = selected contestant is famale
Then numerator entity will
P(A and B) = P(Contestant won prize and Contestant is female)
= Number of female contestant who won prize / Total number of contestant
= 3 /(4+9+3+10)
= 3 / 26
P(A and B) = 0.1153
P(B) = P(contestant is female )
= Number of female contestant / Total number of contestants
= (3+10) / 26
P(B) = 0.5
Now P(A / B) = 
= 0.1153 / 0.5
P(A / B) = 0.2306
The probability that randomly selected contestant won prize given that contestant is female is 0.2306
Converting probability into percentage 23.06%
The percentage that randomly selected contestant won prize given that contestant is female is 23%
Yes but if you need it in mixed number form it’s 1 1/3