Question

Find P(not a 3). X 1 2 3 4P(X) 0.30 0.40 0.15 0.15

Answer 1

From the table, 
P(selecting a 3) = 0.15

which means that,
P(not a 3) = 1 - P(selecting a 3)
P(not a 3) = 1 - 0.15
P(not a 3) = 0.85

Answer is 0.85

Answer 2

Answer: $\text{P(not 3)}=0.85$

Step-by-step explanation:

The given table :

X         1         2         3       4

P(X)  0.30   0.40    0.15   0.15

From the above table we can see that $P(X=3)=0.15$

Also, we know that for any event A , $\text{P(not A)}=1-P(A)$

Therefore,

$\text{P(not 3)}=1-P(X=3)\\\\\Rightarrow\text{P (not 3)}=1-0.15\\\\\Rightarrow\ \text{P(not 3)}=0.85$