If you are telling us to revise the sentence, one error is that there is a double negative. 'not' and 'un' would cancel each other, and the revised sentence 'I wouldn't say he's the nicest guy around, but I've seen him behave kindly before.'
You're getting 1/5 off therefore you are still paying 4/5, which is 11.24
wait didn't you already answer it
Answer: You have to attend a seminar.
Explanation:
'Have to' is used to express general obligations, duties, or necessities (as opposed to 'must', which expresses specific obligations) in the present, the future, or the past. In the future or the past, 'must' and 'need' are always replaced by 'have to'.
Yet, in the negative form, 'don't have to' means there´s no obligation or necessity, but it can be done. ('You don't have to cook' means you can still do it if you fancy to).