2 heads or more in 3 coin toss formula what is the formula to calculate the probabilities of getting 2 heads or more in 3 coin toss ?
i've seen a lot of solution but almost all of them were using method of listing all of possible combination like HHT,HTH,etc
what i am trying to ask is the formula and/or method to calculate this using a formula and
no need to list all of the possible combination.
listing 3 coin toss combination is easy(8 possible combination),but suppose i change the coins to dice or say 20-side dice. that would take a long time to list all the possible combination.

The probability of exactly $2$ heads in $3$  toss is $\binom 3 2 \left(\frac12\right)^2\left(1-\frac12\right)^{3-2}=\frac38 $
The probability of exactly $3$ heads in $3$  toss is $\binom 3 3 \left(\frac12\right)^3\left(1-\frac12\right)^{3-3}=\frac18 $
