x- wiek taty x-5 - wiek ojca 5 lat temu
y - wiek syna y-5-wiek syna 5 lat temu
[tex]\left \{ {{x-5=4(y-5)} \atop {x+y=60}} \right. \\\left \{ {{x-5}=4y-20 \atop {x=60-y}} \right. \\\left \{ {{x-4y=5-20} \atop {x=60-y}} \right\\\left \{ {{x-4y=-15} \atop {x=60-y}} \right.\\60-y-4y=-15\\60-5y=-15\\-5y=-75\\y=15\\x=60-15=45\\\left \{ {{y=15} \atop {x=45}} \right.[/tex]
Odp: Tata ma 45 lat ,a syn 15.
