Question

x + y = 18
2y + x = 16
Find x and y

Answer 1

x + y = 18 ........ (1)
x + 2y = 16........(2)
- - -
_________
0 - y = 2
y = -2
substituting the value of y in equation(1)
x + (-2) =18
x = 20

hope it helps you....

Answer 2

x + y =  18                 ........... i)
x + 2y = 16                ........... ii)

on subtracting i from ii , we get:-
 y = -2

on substituting values in i)
 x - 2 = 18
x = 20