21) The answer is: " 31° F " .
Explanation:
To solve:
Method 1)
| 16 - (-15) | = | 16 + 15 | = | 31 | = 31 .
______________________________
Method 2)
| -15 - 16 | = | -31 | = 31 .
______________________________
22) The answer is: "750 feet below sea level" .
Explanation:
To solve:
- 450 ft - 300 ft = " - 750 ft. " ;
or, " 750 ft. below sea level".
______________________________