[mat]x[/mat] - wiek dziecka
[mat]y[/mat] - wiek mamy
[mat]\left{{{(x-4)*4=y-4}\atop{(x-10)*10=y-10}}\right.[/mat]
[mat]\left{{{4x-16=y-4}\atop{10x-100=y-10}}\right.[/mat]
[mat]\left{{{y=4x-16+4}\atop{10x-100=y-10}}\right.[/mat]
[mat]\left{{{y=4x-12}\atop{10x-100=4x-12-10}}\right.[/mat]
[mat]\left{{{y=4x-12}\atop{10x-4x=-22+100}}\right.[/mat]
[mat]\left{{{y=4x-12}\atop{6x=78}}\right.[/mat]
[mat]\left{{{y=4x-12}\atop{x=13}}\right.[/mat]
[mat]\left{{{y=40}\atop{x=13}}\right.[/mat]