Answer: The total amount the water change was -28 gallons by the end of the week <u>OR</u> 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:
<u>Create you equation:</u>
x = the total amount the water changed
d = the amount of days
x = -4d
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<u>Insert the known information into the equation and solve:</u>