How do you solve the system #3x+y=12# and #y=-x-2# using substitution?

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Answer 1 · 2017-09-29T15:23:34

#x=7#
#y=9#

From the second equation you know what y is equal to. You can substitute this into the first equation.

#3x+(-x-2)=12#

#3x-x-2=12#

#3x-x=12+2#

#2x=14#

#x=7#

Now we can substitute our value of x into the second equation to find y.

#y=-(7)-2#

#y=-7-2#

#y=-9#