# How do solve the following linear system?: # x + y= 12 , 3x + y = -20 #?

##### 2 Answers

Mar 23, 2016

line up the system of equations making sure that the variables are in the same relative positions.

subtract equation 2 from equation 1

this will eliminate the y variable since they both have the same coefficient and same sign.

solve for x

x = -16

now substitute the value for x into either the first or second equation (doesn't matter). A good choice would be to pick the simplest equation of the two and this looks like equation 1.

By substituting x = -16 into eqn,1, you will now be able to solve for the y value.

Mar 23, 2016

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