Question

2x -y = 0
x + y =15
Metodo da adicao !!

Answer 1

2x -y = 0  (i)
x + y =15    (ii)

(i)+(ii)

3x=15
x=5    e  5+y=15  ==>y=10

Answer 2

2x - y = 0
x + y = 15
--------------
3x = 15
x = 15/3
x = 5

x + y = 15
5 + y = 15
y = 15 - 5
y = 10


S={ 5, 10 }