How do you solve #7x+2y= -29# and #-8x+y=43# using substitution?

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Answer 1 · 2017-04-18T06:21:33

#x=-5#
#y=3#

Given -

#7x+2y=-29# -----------------(1)
#-8x+y=43# ------------------(2)

Solve the 2nd equation for #y#

#y=43+8x#

Substitute #y=43+8x# in equation (1)

#7x+2(43+8x)=-29 #
#7x+86+16x=-29 #
#23x=-29-86 =-115#
#x=(-115)/23=-5#
#x=-5#

Substitute #x=-5# in equation (2)

#-8(-5)+y=43 #
#40+y=43#
#y=43-40=3#
#y=3#