Answer: The total amount the water change was -28 gallons by the end of the week OR The total amount the water changed decreased 28 gallons by the end of the week. Depending on how you want to word it.
Hope this helps!
Step-by-step explanation:
Create you equation:
x = the total amount the water changed
d = the amount of days
x = -4d
Insert the known information into the equation and solve:
x = -4d
x = -4(7)
x = -28
