can someone help me with these questions im really stuck

1.)a polgon has 10 sides. The lengths of the sides, starting with the smallest, form an arithmetic series. The perimeter of the polygon is 675cm and the length of the longest side is twice that of the shortest side. Find for this series

a.) the common difference
b.) the first term

2.)The sum ofthe first two terms of an arithmetic series is 47. The thirtieth term of this series is -62. find

a.) the first term of the series and the common difference
b.) the sum of the first 60 terms of the series.

3.)James decides to save some money for the six-week holiday. He saves 1p on the first day, 2p on the second day and 3p on the third day and so on.

a.)How much will he save at the end of the holiday (42 days)
b.)If he carried on, how long would it be before ha has saved £100

thanks