16. Babila received a phone call from his brother in Japan at \( 11: 30 \mathrm{am} \), \( 15^{\circ} \) E.His brothers watch read \( 7: 30 \), at which longitude is his brother located A. \( 80^{\circ} \mathrm{E} \)

To solve the problem, we need to determine the time difference between Babila and his brother. Babila's time is \( 11:30 \, \text{AM} \) (UTC+0), and his brother's watch reads \( 7:30 \) (which we assume is local time in Japan). The time difference is \( 11:30 - 7:30 = 4 \, \text{hours} \). Since Japan is ahead, we can find the longitude using the fact that the Earth rotates \( 15^\circ \) per hour. Therefore, \( 4 \, \text{hours} \times 15^\circ = 60^\circ \). Since Babila is at \( 15^\circ \text{E} \), we need to add \( 60^\circ \) to find his brother's longitude: \( 15^\circ + 60^\circ = 75^\circ \text{E} \). Unfortunately, the answer is not \( 80^\circ \text{E} \), but rather \( 75^\circ \text{E} \). Japan operates on Japan Standard Time (JST), which is UTC+9. So, to confirm: Babila at \( 11:30 \text{AM} \) is indeed \( 4 \, \text{hours} \) behind his brother whose \( 7:30 \, \text{AM} \) puts him at UTC+9, indicating he is around \( 135^\circ \text{E} \). Hence, his brother is at a longitude of approximately \( 135^\circ \text{E} \).