How do you solve this system of equations: $7x + y = 11;- 10x - 5y = 20$ ?

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Answer 1 · 2017-02-06T09:46:40

The method I am using is subsitution.

First, isolate x in the second equation as it is easier to do so;

$-10x = 20 + 5y$

$x = -2 - 0.5y$

Then, replace x in the first equation with the equation above;

$7(-2-0.5y) + y = 11$

$-14-3.5y+y = 11$

$-2.5y = - 25$

$y=- 25/-2.5$

$y=-10$

Now we know y equals to -10

Now, substitute this value to y of the second equation

$-10x-5(-10)=20$

$-10x+50=20$

$-10x = 20-50$

$x=3$

And x equals to 3

How do you solve this system of equations: 7x + y = 11;- 10x - 5y = 207x + y = 11;- 10x - 5y = 20?