Answer:
The percentage error is 14.3% .
Explanation:
Formula

Where
Change in value = |Approx value - Exact value|
As given
Tammy predicted that she would sell 300 bottles of water.
she actually sold 350 bottles.
Exact value = 350
Approx value = 300
Put values in the formula
Change in value = |300 - 350|
Change in value = |-50|
Change in value = 50
Put all the values in the percentage error formula


Percentage error = 14.3%
Therefore the percentage error is 14.3% .