[求助]GWD-11-10--->beautywawa修改标题，见谅！！

A certain quantity is measured on two different scales, the R-scale and the S-scale, that are related linearly.  Measurements on the R-scale of 6 and 24 correspond to measurements on the S-scale of 30 and 60, respectively.  What measurement on the R-scale corresponds to a measurement of 100 on the S-scale?

A.     20

B.     36

C.   48

D.     60

E.      84

两种scale的原点并不在0处，

30=6a+b

60=24a+b，

联立得到a，b，再由100=xa＋b求得x值，

a＝5/3，b＝20，

x＝48