alright so to do this you need some basic algebra
you have to pay an extra 20% of whatever you buy
thus we can make the following equation
.2x+x=20 (since 20 is the amount of money you have)
combining the like terms,
1.2x=20
and finally, dividing both sides by 1.2
x=$16.67
don't forget to check!
.05*16.67=.83 (sales tax makes the total $17.5)
.15*16.67=2.5 (tip makes the total $20)
whaddya you know, it works!
most expensive item you can buy will cost $16.67
hope this helped!
