When 3 fair coins are tossed we have the following possible outcomes:

HHH,

THH, HTH, HHT

TTH, THT, HTT

TTT

The number of all possible outcomes is: 8.

The outcomes that have at least 2 tails are 4:

TTH, THT, HTT, TTT

The outcomes that have exactly 2 tails are 3:

TTH, THT, HTT

The probability of getting at least 2 tails when 3 fair coins are tossed is:

p = 4/8

p = 0.5

The probability of getting exactly 2 tails when 3 fair coins are tossed is:

p = 3/8

p = 0.375