1.Archie, Betty and Coach bought a radio. Archie paid the least amount of money, Coach paid twice as much as Archie, and Betty paid the most. Archie paid seventy dollars less than the difference between what Betty and Coach paid. If Archie had paid twice as much as he did pay, Betty and Coach would have each paid ten dollars less. Which of the following equals the amount Betty paid?

Ans: c, 但没有读懂答案

2.

If -4<=A<=8

-7<=B<=6

-3<=C<=2 <= ( 表是小于且等于) then the least possible value of AB+ BC =

a. 49, b -42, c, -70, d, -72, e, -74

ans: c, my E, why ?

第一题，以此以他们得名字首字母代替他们，得2个关系式1)c=2a,2)b-c=a+70;而且数a加倍，c和b就可以减少10，推出a=20,带入前面得方程可以得，b=130

感谢感谢！