x + 2y = 11

2x + y = 31

So the system of two equations with 2 unknowns is

Solve that system by substitution or elimination.  If you have trouble, ask me
for help in the space below and I'll get back to you be email.

Edwin

From the condition, you have these two equations in two unknowns


     x + 2y = 11     (1)

    2x +  y = 31     (2)


From equation (1), express  x = 11 - 2y  and substitute it into the second equation. You will get


   2*(11-2y) + y = 31.


Simplify and solve for y


    22 - 4y + y = 31

    -3y         = 31 - 22

    -3y         = 9

      y         =  = -3.


Then  x = 11 - 2y = 11 - 2*(-3) = 11 + 6 = 17


ANSWER.  x = 17,  y = -3.