How do you solve #9x - y = 317# and #10x - 11y = 550# using substitution?

1 Answer
Alan P.
Jun 9, 2016

#(x,y)=color(green)(""(33,-20))#
(see below for solution by substitution)

Explanation:

Given
[1]#color(white)("XXX")9x-y=317#
[2]#color(white)("XXX")10x-11y=550#

We can re-arrange [1] as
[3]#color(white)("XXX")y=9x-317#

Using [3] we can substitute #9x-317# for #y# in [2]
[4]#color(white)("XXX")10x-11(9x-317)=550#

[5]#color(white)("XXX")10x-99x=550-3487#

[6]#color(white)("XXX")89x=2937#

[7]#color(white)("XXX")x=33#

Using [7] we can substitute #33# for #x# in [1]
[8]#color(white)("XXX")9(33)-y=317#

[9]#color(white)("XXX")297-y=317#

[10]#color(white)("XXX")y=-20#

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