Odpowiedź:
a) x + y = 10
2x + y = 13
------------------------
-x = -3
x = 3
y = 10 - 3 = 7
b) x + 2y = 8
3x + 2y = 12
--------------------------
-2x = -4
x = 2
2y = 8 - 2
2y = 6
y = 3
c) x + 2y = 5
x + 3y = 7
------------------------
-y = -2
y = 2
x + 4 = 5
x = 1
d) x + y = 7
x + 3y = 17
------------------------------------
-2y = -10
y = 5
x + 5 = 7
x = 2
