Zoe Paid $18.60 in sales tax and tips for her dinner the sales tax rate is 11% and she tipped 20%

The cost of the dinner before other costs is $14.20

Step-by-step explanation:

To solve this, we write the following equation:

x +.11x +.20x = 18.60

This is because in addition to paying for the dinner (x), she also has to pay 11% of it and another 20% of it. Now we can combine like terms and solve.

1.31x = 18.60

x = 14.20