P(X = k) = \binom{n}{k} p^k (1-p)^{n-k}
n = 6
k = 4
p = 0.5
\binom{6}{4} = 15
P(X = 4) = 15 \cdot (0.5)^4 \cdot (0.5)^2
P(X = 4) = 15 \cdot (0.5)^6
P(X = 4) = 15 \cdot \frac{1}{64}
P(X = 4) = \frac{15}{64}
P(X = 4) \approx 0.2344
P(X = 4) = \frac{15}{64}