Probability

I am having trouble figuring out the probability with medications.
WE have No help Help
Drug 22 47
Placebo 31 20
What is the probabilty
a.the participants perceived that their “medication”
helped if they received the drug?
b. the participants perceived that their “medication”
helped if they received the placebo?
c. the participants perceived that their “medication”
helped?
I would believe they would all be out of 120 but it seems like I am missing something.

have------------------no help-----------help
drug---------------------22---------------47
placebo------------------31---------------20

a)
no. received drug=22+47=69
no. helped=47
Prob= 47/69

b)
no. received placebo=51
no. helped=20
Prob.=20/51

c)
no helped=20+47=67
total tested=120
Prob= 67/120

Arthur