Zoe paid $18.60 in sales tax and tips for her dinner
Sales tax + tips for dinner = 18.60
The sales tax rate is 11%, and she tipped 20%. Given that the sales tax does not apply to the tip, and the tip is based on the price of the dinner before sales tax.
Let x be the original price
Sales tax = 11% * original price = 0.11 * x= 0.11x
Tips for dinner = 20% * original price = 0.20 * x = 0.2x
We know Sales tax + tips for dinner = 18.60
0.11x + 0.2x = 18.60
0.31x = 18.60
Divide by 0.31 on both sides
x = 60
$60 was the price of Zoe's dinner, before sales tax and tip.