How do you solve #x=-4y# and #3x+2y=20#?

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Answer 1 · 2017-02-16T21:37:02

See the entire solution process below:

Step 1) Because the first equation is already solved in terms of #x#, substitute #-4y# for #x# in the second equation and solve for #y#:

#3x + 2y = 20# becomes:

#3(-4y) + 2y = 20#

#-12y + 2y = 20#

#-10y = 20#

#(-10y)/color(red)(-10) = 20/color(red)(-10)#

#(color(red)(cancel(color(black)(-10)))y)/cancel(color(red)(-10)) = -2#

#y = -2#

Step 2) Substitute #-2# for #y# in the first equation and calculate #x#:

#x = -4y# becomes:

#x = -4 * -2#

#x = 8#

The solution is: #x = 8# and #y = -2# or #(8, -2)#