Мастер за 1 час изготавливает 48 деталей,а ученик 22 детали. за какое время работая вместе,они изготовят 280 деталей?

Помогите пожалуйста.

Open the brakets.

1) He (wake up) ...at 7 a.m. every morning.
2) He never (see) ...a monkey.
3) She (have) ...breakfast when he (walk) ...in.
4)The mailman just (deliver) ...the mail.
5) After he (park) the car he (lock) ...it.
6) I (not go) to party if she (not invite) ...Me.
7) Before she (invite) ...me to the party she (call) ...My Friends.
8) When she (walk) ...in they (watch) ...videofilms.
9) Before she (make) ...dinner she (go) ...shopping.
10) She (make) ...a dress by 10 p.m. yesterday. 

Кау узнать что число делится на 3,число делится на 3 если сумма кго цифр делится на 3