A math student has a plan to solve the following system by the elimination method. To eliminate the x-terms, he wants to multiply the top equation by 7. What should he multiply the second equation by so that when he adds the equations, the x-terms are eliminated? -3x-7y=-56 -7x+10y=1

$\begin{cases}-3x-7y=-56\\ -7x+10y=1\end{cases}\Leftrightarrow \begin{cases}21x+49y=392\\ -21x+30y=3\end{cases}\Rightarrow 79y=395\Rightarrow y=5\Rightarrow x=7$

Умножить нужно первое уравнение на -7, а второе на 3

-3

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