:законы сложения дробей 2/45+[3/45+7/9] [3/7+5/14]+1/14 7/15+[2/15+1/5] 3/16+[1/16+5/8] [1/13+1/14]+12/13

2/45+[3/45+7/9]=2/45+3/45+7/9=5/45+7/9=1/9+7/9=8/9

[3/7+5/14]+1/14=3/7+5/14+1/14=3/7+6/14=3/7+3/7=6/7

7/15+[2/15+1/5] =7/15+2/15+1/5=9/15+1/5=3/5+1/5=4/5

3/16+[1/16+5/8] =3/16+1/16+5/8=4/16+5/8=2/8+5/8=7/8

[1/13+1/14]+12/13=1/13+1/14+12/13=13/13+1/14=1+1/14=1 1/14