问答题 Four years ago, Jane was twice as old as Sam. Four years on from now, Sam will be 3/4 of Jane's age. How old is Jane now?
【正确答案】
【答案解析】12 years old 设Jane现在是x岁，Sam现在是y岁，根据题意可得下列议程式：x-4=2 (y-4)；3/4(x+4)=y+4得x=12，所以Jane现在是12岁。