Percentage of tip that needs to be given for hair cut = 15%
Amount of tip is calculated without sales tax.
Amount taken for the hair cut = 20
Amount of sales tax taken = 4.75
Then
Amount of tip given = (15/100) * 20
= 300/100
= 3
So the total amount required for the hair cut = 20 + 4.75 + 3
= 27.75
So 25 is insufficient amount to cover the hair cut cost with tip and sales tax. The actual amount required to cover the total cost is 27.75