Question

in ograda unui gospodar sunt gaini si oi. in total, sunt 68 capete si 180 de picioare.

Cate gaini si cate oi are gospodarul ?

Answer 1

x- gaini
y= oi

x+y=68           /-2
2x+4y=180

-2x-2y=-136
2x+4y=180
-----------------(+)
/          2y=44
y=44:2
y=22 oi

x+22=68
x=68-22
x=46 gaini

Answer 2

x-numarul de gaini, y-numarul de oi;
x+y=68      ⇔     x=68-y          ⇔ x=68-y             ⇔x=68-y        ⇔x=68-y
2x+4y=180 ⇔ 2*(68-y)+4y=180 ⇔136-2y+4y=180 ⇔2y=180-136⇔2y=44

x=68-y ⇔x=68-22=46
y=22   ⇔y=22
R-s: Gospodarul are 46 gaini si 22 oi.