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