Competition problem — Algebra — Maths Olympiad Prep

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Algebra Difficulty 1.8 Junior Find the answer

If $\begin{tabular}{r|l}a&b \\ \hline c&d\end{tabular} = \text{a}\cdot \text{d} - \text{b}\cdot \text{c}$ , what is the value of $\begin{tabular}{r|l}3&4 \\ \hline 1&2\end{tabular}$ ?

Pick one

Solution

Plugging in values for $a$ , $b$ , $c$ , and $d$ , we get
$a=3$ ,
$b=4$ ,
$c=1$ ,
$d=2$ ,
$a\times d=3\times2=6$
$b\times c=4\times1=4$
$6-4=2$
$\boxed{E}$

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Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic and difficulty added by this site.