Условие:
doesn't brushes
doesn't brushs
doesn't brush
don't brush
He \square his teeth
twice a day.

doesn't brushes
doesn't brushs
doesn't brush
don't brush
He \square his teeth
twice a day.
Шаг 1. Видим, что подлежащее – местоимение «He», оно в третьем лице единственного числа, поэтому при отрицательной форме ...