求解XDF数学讲义上的几道题！！！！！！！！！！！

djj629

1 If each of the 12 teams participating in a certain tournament plays exactly one game with each of the other teams, how many games will be played?
A144  B132 C66  D33  E23
答案C 本题诗对tournament plays 不理解  记得还有一个round match是什么意思啊 ？

2 From May 1 to May 30 in the same year, the balance in a checking account increased. what was the balance in the checking account on May 30?
(1)If, during this period of time,the increase in the balance in the checking account had been 12 percent , then the balance in the account on May 30 would have $504
(2)During this period of time, the increase in the balance in the checking account was 8 percent
答案C

3 A parent estabished a college fund for his daughter.Each year the parent made a contribution to the fund, and each year he increased his contribution by a constant amount. If he made a contribution of $800 in the first year, by what amount did the parent increase his contribution to the fund each year?
(1)The parent's contribution to the fund in the 18th year was $7600.
(2)The parent's contribution to the fund in the 7th year was twice what it was in the 3rd year.
答案D  这题有些弄不懂题意啊 万分感谢了 考试在即。。。。。。