How do you solve $5x – 6y = 21$ and $x - 2y = 5$ using substitution?

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Answer 1 · 2016-03-05T08:00:23

Solution is $x=3$ and $y=-1$

To solve $5x–6y=21$ and $x−2y=5$ using substitution, we first get value of $x$ from second equation and put it in first equation.

From second equation $x−2y=5$ , we get $x=5+2y$ ... (A)

Hence second equation becomes

$5(5+2y)–6y=21$ i.e. $25+10y-6y=21$ or

$4y=21-25=-4$ and hence $y=-4/4=-1$ .

Now putting this in (A), we get $x=5+2xx(-1)$ or

$x=5-2=3$

Hence solution is $x=3$ and $y=-1$

How do you solve 5x – 6y = 21 5x – 6y = 21 and x - 2y = 5x - 2y = 5 using substitution?