How do you solve x = y - 8 & -x - y = 0? Algebra Systems of Equations and Inequalities Systems Using Substitution 1 Answer José Roberto Pereira Oct 18, 2015 #x=-4# #y=4# Explanation: #y=x+8# (1) #y=-x# (2) Subtracting (1) - (2): #0=2x+8# #2x=-8# #x=-8/2=-4# #y=-(-4) =4# Answer link Related questions How do you solve systems of equations using the substitution method? How do you check your solutions to a systems of equations using the substitution method? When is the substitution method easier to use? How do you know if a solution is "no solution" or "infinite" when using the substitution method? How do you solve #y=-6x-3# and #y=3# using the substitution method? How do you solve #12y-3x=-1# and #x-4y=1# using the substitution method? Which method do you use to solve the system of equations #y=1/4x-14# and #y=19/8x+7#? What are the 2 numbers if the sum is 70 and they differ by 11? How do you solve #x+y=5# and #3x+y=15# using the substitution method? What is the point of intersection of the lines #x+2y=4# and #-x-3y=-7#? See all questions in Systems Using Substitution Impact of this question 1375 views around the world You can reuse this answer Creative Commons License