Răspuns :
156-102=54lei(3mingi de football)
=>1 minge de football = 54 : 3 = 18
x-mingi de handbal
y-mingi de fotbal
[tex]2x + 4y = 102 \\ 2x + 7y = 156 \\ - 2x \\ 4y - 7y = - 54 \\ - 3y = - 54 \\ y = 18 \\ 2x + 72 = 108 \\ 2x = 108 - 72 \\ 2x = 36 \\ x = 18[/tex]
y-mingi de fotbal
[tex]2x + 4y = 102 \\ 2x + 7y = 156 \\ - 2x \\ 4y - 7y = - 54 \\ - 3y = - 54 \\ y = 18 \\ 2x + 72 = 108 \\ 2x = 108 - 72 \\ 2x = 36 \\ x = 18[/tex]