yesterday evening, while my mother……( cook ) in the kitchen, my father…..( watch) the news on TV

→Yesterday evening, while my mother was cooking in the kitchen, my father was watching the news on TV.

$\circ$ was/were + V-ing

my mother chuyển sang was cooking

my father chuyển sang  was watching

thì QK tiếp diễn

→while + QK tiếp diễn