У Оли осталось 20 руб.потратила она 30 рублей.сколько было у Оли денег,если у Тани было -50 руб

what does the internet provide?what is the meaning of knowledge?what can help students define themselves in class?which students like school?why some students hate school?where can you take part in?what do clubs organise?what is the second main social environment for young people after home?where do you go with your classmate?

Если Оля потратила 30, а осталось 20, значит у нее вначале было 30 + 20 = 50 рублей.