This plus that is twenty-one,this minus that is five.What is this and what is that?

设:this=x that =y
列方程:x+y=21
x-y=5
解方程得:x=13 y=8
即:this=13 that=8
因此答案为:This is thirteen and that is eight .
楼主,烦请你把此问的分类设置为:教育/科学下的"英语考试".请拿出综合算式x+y=21 x=21-yx-y=5x=5+y21-y=5+y2y=16y=8x=5+8=13