I'd write the essay yourself so you don't get busted for cheating, just look up what both of them are and go from there.
Esta no es una pregunta matemática, vaya a la sección "Salud"
I'm assuming you meant shirts instead of shorts for the older brother.
1/6 + 3/6 = 4/6
4/6 of the shirts belong to his brothers
(or 2/3 if you simplify the fraction)