How much do 8 sandwiches, 2 cups of coffee, and 20 donuts cost? And how much do 9 sandwiches, 3 cups of coffee, and 21 donuts cost?

## Solution

From the condition, it is clear that 8 sandwiches, 2 cups of coffee, and 20 donuts cost $2 \cdot 1.69 = 3.38$, and 9 sandwiches, 3 cups of coffee, and 21 donuts $-3 \cdot 1.26 = 3.78$. The difference between these amounts will give exactly the cost of a sandwich, a cup of coffee, and a donut.

## Answer

40 cents.
Three cowboys walked into a saloon. One bought 4 sandwiches, a cup of coffee, and 10 donuts for a total of $1.69. The second bought 3 sandwiches, a cup of coffee, and 7 donuts for $1.26. How much did the third cowboy pay for a sandwich, a cup of coffee, and a donut?