Question

At a restaurant, you eat 2 taco salads and drink 2 glasses of iced tea. Your friend eats 1 taco salad and drinks 1 glass of ice tea. You get charged $11 and your friend $6.50. Can you determine the price of taco salads and iced tea? Explain.

Answer 1

Let x be taco salads, and y be drinks.
The equations are as follows:
1) 2x+2y=11
2) x+y=6.50
Use 2) to isolate for a variable, for example:
3) y=6.50-x
Using 3), substitute it back into 1) to solve for x.
2x+2(6.50-x)=11
2x-2x+13=11
The x's cancel out, leaving you with:
13=11
This is not true, and therefore you cannot determine the prices of the taco salads or iced tea.