（1/4-0.1÷2）*5/13+1÷1又1/12
=(1/4-1/20)x5/13+ 1x12/13
=1/5x5/13+12/13
=1/13+12/13
=1
25*1/3*2/5*3/10
=(25x2/5)x(1/3x3/10)
=10x1/10
=1
如果本题有什么不明白可以追问,