For any positive integer n, the sum of the first n positive integers equals [n(n+1)]/2.  What is the sum of all the even integers between 99 and 301?

请各位大侠帮忙把题目翻译一下~把解法和步骤也写下哈·~小女子感激不尽还有

Running at their respective constant rates, machine X takes 2 days longer to produce w widgets than machine Y.  At these rates, if the two machines together produce 5/4 w widgets in 3 days, how many days would it take machine X alone to produce 2w widgets?

这道题怎么算啊·~各位大侠帮帮忙吧！！最怕这种涉及效率的题目了

Running at their respective constant rates, machine X takes 2 days longer to produce w widgets than machine Y.  At these rates, if the two machines together produce 5/4 w widgets in 3 days, how many days would it take machine X alone to produce 2w widgets?

这道题怎么算啊·~各位大侠帮帮忙吧！！最怕这种涉及效率的题目了