(i) Let \(P(BH)\) be the probability that Khalid hurts himself while riding his bicycle, and \(P(SH)\) be the probability that he hurts himself while riding his skateboard. We have:

\(P(BH) = 0.6 \times 0.05 = 0.03\)

\(P(SH) = 0.4 \times 0.75 = 0.3\)

The probability that Khalid hurts himself on any particular day is:

\(P(H) = P(BH) + P(SH) = 0.03 + 0.3 = 0.33\)

(ii) We need to find \(P(S|H)\), the probability that Khalid is riding on his skateboard given that he hurts himself. Using the formula for conditional probability:

\(P(S|H) = \frac{P(S \cap H)}{P(H)}\)

\(P(S \cap H) = P(SH) = 0.3\)

\(P(H) = 0.33\)

Thus, \(P(S|H) = \frac{0.3}{0.33} = \frac{10}{11} \approx 0.909\)