英语翻译1 the tenth term of an arithmetic series is 67 and the s

英语翻译
1 the tenth term of an arithmetic series is 67 and the sum of the first twenty terms is 1280.find the common difference ,d and the first term a .
2 if the first term of an arithmetic sequence is 3 and the hundredth tern is 307,then find the sum of the first 100 terms.
3 an arithmetic sequence has thirteen terms whose sum is 143.the third term is 5.find the first term