Zelie planned for a square pool to have a side length of 28 ft but found that it needs to be 14 ft long to fit in her backyard. She found the change of scale below.

StartFraction 28 feet minus 7 over 14 feet minus 7 EndFraction = StartFraction 21 over 7 EndFraction

Which is Zelie’s error?
Zelie should have divided both numbers by 14.
Zelie should have written the ratio as StartFraction 28 feet over 7 feet EndFraction.
Zelie should have written the ratio as StartFraction 14 feet over 28 feet EndFraction.
Zelie should have subtracted 14 from both numbers.