Eva

When Eve bought eight packages of cookies, 4 CZK left her. If she wanted to buy ten packages, she would have to borrow 20 CZK. How much money does Eve have in her wallet?

Final Answer:

x =  100

Step-by-step explanation:

$$\begin{gathered} 8y=x-4 \\ 10y=x+20 \\ 8\cdot y=x-4 \\ 10\cdot y=x+20 \\ x-8y=4 \\ x-10y=-20 \\ Row2-Row1\to Row2 \\ -2y=-24 \\ y=\frac{-24}{-2}=12 \\ x=4+8y=4+8\cdot 12=100 \\ x=100 \\ y=12 \end{gathered}$$

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