first,we should do it in the last digit.because 1 is not able to minus 5.we borrow 1 from the former digit,so the digit has turned into 4.and the borrowed 1 should be converted into 10 to suit the last digit.we plus it with the origin number,10+1=11.therefore,the result of the last digit is 11-8=3.and the former digit is 4-3=1.
so the result is 13.
下一题的话..我不知道你是要哪种程度的解释啊..说 清楚点..