How do you solve the system of equations #x- 9y = 20# and #10x - 18y = - 16#?

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Answer 1 · 2016-11-01T19:28:46

Please see the explanation. #x = -7 and y = -3#

Given:

#x - 9y = 20# [1]
#10x - 18y = -16# [2]

Multiply equation [1] by -2 and add to equation 2:

#10x - 2x - 18y + 18y = -16 - 40#

#8x = -56#

#x = -7#

Substitute -7 for x into equation [1]

#-7 - 9y = 20#

#-9y = 27#

#y = -3#

Check:

#-7 - 9(-3) = 20#
#10(-7) - 18(-3) = -16#

#20 = 20#
#-16 = -16#

This checks