x+y=8 2x+y=11

Question

Solve for y using substitution

Answer 1

  X + Y = 8

2X + Y = 11

Step 1: Solve for one of the variables in terms of the other using either one of the equations provided

              X + Y = 8  -------------->   Y = 8 - X

Step 2: Use your definition for Y (which is defined in terms of X here) and substitute in the unused equation.

     1.        2X + (8 - X) = 11

     2.        X + 8 = 11 

     3.        X = 11 - 8 = 3 

Step 3: Substitute X = 3 in the original first equation you used to solve for Y in terms of X

                Y = 8 - 3 = 5

Answer: X = 3      Y = 5