SOLUTION: Solve the problem of equations by substitution method X+7y=31 2x+3y=7

Algebra.Com
Question 1051834: Solve the problem of equations by substitution method
X+7y=31
2x+3y=7
Found 2 solutions by ikleyn, solver91311:
Answer by ikleyn(52778)   (Show Source): You can put this solution on YOUR website!
.
Solve the problem of equations by substitution method 

 x + 7y = 31   (1)
2x + 3y =  7   (2)

From (1), express x = 31-7y, and then substitute it into (2). You will get

2*(31-7y) + 3y = 7.

Simplify:

62 - 14y + 3y = 7,

-14y + 3y = 7 - 62,

-11y = -55,

y =  = 5.

Then x = 31-7y = 31-7*5 = 31-35 = -4.

Answer.  x = -4, y = 5.

On solving systems of linear equations in two unknowns see the lessons
    - Solution of a linear system of two equations in two unknowns by the Substitution method
    - Solution of a linear system of two equations in two unknowns by the Elimination method
    - Solution of a linear system of two equations in two unknowns using determinant
    - Geometric interpretation of a linear system of two equations in two unknowns
    - Solving word problems using linear systems of two equations in two unknowns
in this site.


Answer by solver91311(24713)   (Show Source): You can put this solution on YOUR website!


What you ask cannot be done. You have two equations and three variables, namely X, x, and y. X and x are not now, never have been, and never will be the same thing.

However, going on the assumption that you were just being sloppy and actually meant:





Solve the first equation for :



Substitute the RHS expression in place of in the second equation and then solve for



... and then solve for . Once you know , substitute that value back into either original equation and solve for .

John

My calculator said it, I believe it, that settles it
RELATED QUESTIONS

solve each system of equations by the substitution method 2x-y=-7... (answered by mananth)
Solve the system of equations by using the substitution method. {2x – 3y=14 {y=x - 5 (answered by mananth,jorel1380)
solve the system of equations by using the substitution method 2x-3y=9,... (answered by jim_thompson5910)
The question is: Solve the system of linear equations using substitution method... (answered by checkley75)
solve each system of equations by substitution method 8x+3y=-7 (answered by checkley79)
Solve by the substitution method: 7y - x = 32 x =... (answered by user_dude2008)
Solve the following system of equations by using the substitution method. Y=6x-11... (answered by Alan3354)
Solve the systems of equations by the substitution method. x-6y=33... (answered by saifoo.khan)
Can you help me to solve these two equations by using the substitution method. 2x + 4y (answered by mananth)