Sally estimated that the cost of a new fish tank would be $45. the actual cost was 37.79. what was the percent error between sally's estimate and the actual amount

Actual cost of the fish tank that Sally wanted to buy = $37.79
The price that Sally thought would have to pay for buying the fish tank = $45
Then
Amount of money miscalculated by Sally = (45 - 37.79) dollars
                                                                   = 7.21 dollars
Now
Percentage of error made by Sally while calculating = (7.21/37.79) * 100
                                                                                   = (721/3779) * 100
                                                                                   = 72100/3779
                                                                                   = 19.079
                                                                                   = 19.08
So Sally made an error of 19.08% while calculating the price of the fish tank.