Put the verbs in brackets into the present indefinite present continuous present perfect or present perfect continuois tenses helen(to learn) english at the institute. she (learn) english since last summer/ theu are busy now. they (to discuss) an important question. they (to discuss)in since 5 0"clock . where is peter? -he (towork) in the library.-he (to work) long? -yes, he (to work) there for ten days. he (to teach) french. he is a very experienced teacher . he (to teach) french for fifteen years. i (to know) peter well.- since when you (to know) him? i (to know )him since 1940

Learned / has been learning
are discussing / have been discussing
is working / has he worked a long? / he has been working
teaches / has been teaching
know / have you known  / have known

Честно говоря, меня немного поставила в тупик эта часть: He (to work) long?
Возможно ты что-то пропустила там. По логике должен был быть вопрос "Как долго он уже работает" - "How long has he worked?" Но на этот вопрос не может быть ответа, который следует дальше (-Yes, he...) Так что здесь возможен косяк. Остальное, надеюсь, сделал правильно))