How do you solve the system #y=5x-7 # and #-3x-2y=-12# by substitution?

1 Answer
Tessalsifi
Jun 3, 2015

We know that #y=5x-7# so we are just going to replace the #y# in the other equation :

#-3x-2y=-12#
#-3x-2*(5x-7)=-12#
#-3x-10x+14=-12#
#-13x=-12-14# ( we substract #14# on each side )
#-13x=-26#
#x=2# ( we divide by #-13# on each side )

Now that we have #x#, we can find #y# with the first equation :

#y=5x-7#
#y=5*2-7#
#y=10-7#
#y=3#

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