There are many ways of solving the set of equations x + y = 30 and x - y = 2 for x and y.
From x +y = 30 we get x = 30 - y
Now substitute this in the equation x - y = 2
30 - y - y = 2
-2y = -28
y = 14
As x = 30 - y = 30 - 14 = 16
The required solution of the set of equations is x = 16 and y = 14
Toodles~