Answer:
(-8) + (+17) = -8 + 17 = 9
Step-by-step explanation:
Level of water in the first week = - 8 (the negative sign represents a decrease in inches, of the level of water)
Level of water during the second week = + 17 (the positive sign represents an increase, in inches, of the level of water).
These changes in the level of water can be modelled as sum of a positive and a negative integer as follows:
(-8) + (+17)
When adding a negative and a positive integer value, subtract the smaller value from the greater value, and retain the sign of the value that is greater.
17 is greater than 8. Therefore, subtract 8 from 17, and retain the sign of 17.
Thus:
(-8) + (+17) = -8 + 17
= 9
