Dave pays $15 and tax is $1.2 so dave spent a total of $16.20.
Mel pays $20 and tax is $1.6 so Mel spent a total of $21.60.
All you need to do is convert the percent to a decimal, so take 8 and divide by 100 and you get 0.08. then you need to multiply the cost by the tax so 15*0.08=1.2 then you just add tax to original amount 15+1.2=16.2
:)
