Question

几道分数数学题求解一下，要有过程！

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Answer 1

25x7/13-7x12/13
=25x7/13-12x7/13
=7/13x(25-12)
=7/13x13
=7

(2013+2014x2012)/(2013x2014-1)
=[2013+(2013+1)(2013-1)]/(2013x2014-1)
=(2013+2013²-1)/(2013x2014-1)
=[2013x(1+2013)-1]/(2013x2014-1)
=(2013x2014-1)/(2013x2014-1)
=1

（1+1/2+1/3)(1/2+1/3+1/4)-(1+1/2+1/3+1/4)(1/2+1/3)
=(1+1/2+1/3)(1/2+1/3)+1/4(1+1/2+1/3)-(1+1/2+1/3)(1/2+1/3)-1/4(1/2+1/3)
=1/4+1/4(1/2+1/3)-1/4(1/2+1/3)
=1/4

1/又1/3-7/12+9/20-11/30+13/42-15/56
=1+1/3-1/3-1/4+1/4+1/5-1/5-1/6+1/6+1/7-1/7-1/8
=1-1/8
=7/8

15又3/11x1/7
=(14+14/11)x1/7
=14x1/7+14/11x1/7
=2+2/11
=2又11分之2