Expensive 82581

Five bottles of white wine and six bottles of red wine cost 1410 CZK. A bottle of red wine was CZK 15 more expensive than a bottle of white wine. How many crowns will we pay for two white and two red wine bottles?

Correct answer:

x =  510 Kc

Step-by-step explanation:

$$\begin{gathered} 5a+6b=1410 \\ b=15+a \\ 5\cdot a+6\cdot b=1410 \\ b=15+a \\ 5a+6b=1410 \\ a-b=-15 \\ Row2-\frac{1}{5}\cdot Row1\to Row2 \\ 5a+6b=1410 \\ -2.2b=-297 \\ b=\frac{-297}{-2.2}=135 \\ a=\frac{1410-6b}{5}=\frac{1410-6\cdot 135}{5}=120 \\ a=120 \\ b=135 \\ x=2\cdot a+2\cdot b=2\cdot 120+2\cdot 135=510\text{Kc} \end{gathered}$$

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