To find the probability that an adult in the USA has Stage 2 high blood pressure (systolic BP \( \geq 160 \) mmHg), we calculate:
\[
P = \Phi(Z_{end}) - \Phi(Z_{start}) = \Phi(\infty) - \Phi(1.5385) = 0.062
\]
Thus, the probability of Stage 2 high blood pressure is:
\[
\boxed{P = 0.062}
\]
Next, we determine the probability that an adult has Stage 1 high blood pressure (systolic BP between \( 140 \) and \( 160 \) mmHg):
\[
P = \Phi(Z_{end}) - \Phi(Z_{start}) = \Phi(1.5385) - \Phi(0.7692) = 0.1589
\]
Therefore, the probability of Stage 1 high blood pressure is:
\[
\boxed{P = 0.1589}
\]
To find the systolic blood pressure corresponding to the 30th percentile, we use the inverse of the cumulative distribution function:
\[
\text{Systolic BP} = 106.3656 \text{ mmHg}
\]
Thus, the systolic blood pressure at the 30th percentile is:
\[
\boxed{BP = 106.3656 \text{ mmHg}}
\]
- Probability of Stage 2 high blood pressure: \( \boxed{0.062} \)
- Probability of Stage 1 high blood pressure: \( \boxed{0.1589} \)
- Systolic BP at the 30th percentile: \( \boxed{106.3656 \text{ mmHg}} \)