Из бака отлили 1/5 часть бензина,потом 15% его общей ёмкости.После этого в баке осталось 65л. Какова ёмкость бака? Решение,пожалуйста.

Перевод текста(в переводчике белеберда получается):The Edinburgh military tattoo takes place every August and September. For 90 minutes on five or six nights a week, 600 people perform in the square in front of the Castle. One of the most modest and yet one of the best known monuments in Edinburgh is a monument to dog called Bobby. The dog belonged to John Gray. When he died Bobby lived near his grave for twenty-six years. Later Bobby was buried near his master and his statue in the Old Town has become a symbol of devotion. The Old Town is a striking contrast to New Town with its white and beautiful streets. Princes Street is the most beautiful street of the New Town. It is Edinburgh’s popular shopping centre. Princess Street lies between the New Town and the Old Town. The modern town is on the lower side, the old one – on the higher. They look at each other across the valley under Scotland’s blue sky.

Накиньте пару предложений о роли местоимении в жизни человека))))

1.Упростите выражение: tg40'+tg20' / 1-tg40' * tg20'

2.Решите уравнение: sin x * cos3x + sin3x * cosx = 1

3. Вычислите cos(альфа+бетта), если cosальфа = -3/5 и ПИ<альфа<3ПИ/2 , sinбетта= 8/17 и ПИ <бетта<Пи