【Answer】: 1. Newborn (up to 4 weeks old): 100 ≤ x ≤ 205
2. Infant (4 weeks to 1 year): 100 ≤ x ≤ 180
3. Toddler (1 to 3 years): 98 ≤ x ≤ 140
4. Preschool (3 to 5 years): 80 ≤ x ≤ 120
5. School Age (5 to 12 years): 75 ≤ x ≤ 118
6. Adolescent (13 to 18 years): 60 ≤ x ≤ 100
7. Adults (18+): 60 ≤ x ≤ 100
【Explanation】: The question asks for the normal heart rate range for different age groups. The heart rate is given as a range of beats per minute (bpm). The inequality is used to represent this range. For each age group, the lower limit of the heart rate range is the minimum heart rate and the upper limit is the maximum heart rate. Therefore, the inequality for each age group is written as "lower limit ≤ x ≤ upper limit", where x represents the heart rate. For example, for the newborn age group, the heart rate range is 100-205 bpm, so the inequality is 100 ≤ x ≤ 205. Similarly, the inequalities for the other age groups are written.
