x+y=38; x-y=26-x

x + y = 38

x - y = 26 - x

x + x - y = 26

2 x - y = 26

x - y = 26 - x

is equivalent to :

2 x - y = 26

Your system is :

x + y = 38

2 x - y = 26

Using Substitution Method.

Expressing y as a function of x (from the first equation)

x + y = 38

y = 38 - x

Substituting this expression into the second equation:

2 x - y = 26

2 x - ( 38 - x ) = 26

2 x - 38 + x = 26

2 x + x = 26 + 38

3 x = 64 Divide both sides by3

x = 64 / 3

y = 38 - x

y = 38 * 3 / 3 - 64 / 3

y = 114 / 3 - 64 / 3

y = 50 / 3