Given that C⊂D means C is present entirely inside D. Which is shown below.
P(
C
D
)=
P(C∩D)
P(D)
=
P(C)
P(D)
As C∩D means common part of events C and D which is equal to C.
0≤P(D)≤1 ∴
P(C)
P(D)
≥P(C) Note: Here we are dividing with P(D) which is ≤1 and ≥0, as we know on dividing with a number n in the range 0≤n≤1 we get always more than or equal to the original number.