based on illustrative mathematics http://tasks.illustrativemathematics.org/content-standards/6/EE/A/3/tasks/997
Question 1
1.
Anna enjoys lunch at a restaurant in Washington, D.C., where the sales tax on meals is 10%. The tax is calculated on the cost of the meal without tax or tip. Anna's 15% tip is also based on the cost before tax or tip.
She spends a total of $27.50. What is the cost of her meal without tax or tip?