How do you solve 3x+y=21 and x+y=1? Algebra Systems of Equations and Inequalities Systems Using Substitution 1 Answer Binayaka C. Jan 29, 2016 x=10;y=−9 Explanation: 3x+y=21 (1) x+y=1 (2) Subtracting (2) from (1) we get 2x=20orx=10 andy=1−10=−9[Answer] 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=14x−14 and y=198x+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 2746 views around the world You can reuse this answer Creative Commons License