bebrbobr 1) 1/4 + 3/5 =
1/4*5 + 3/5*4=5/20 + 12/20=17/20=17:20=0,85
2) 9/11 - 2/5=
9/11*5 - 2/5*11=45/55-22/55=23/55
3) 13/16-9/32=
13/16*2 - 9/32*1= 26/32-9/32=17/32
4) 3/28+5/14=
3/28*1 + 5/14*2= 3/28 + 10/28=13/28
5) 14/15 - 7/10=
14/15*2 - 7/10*3=28/30 -21/30 = 27/30=27:30=0,9
6) 3/8 + 1/6=
3/8*3 + 1/6*4=9/24 + 4/24= 13/24
7) 9/25 - 7/20=
9/25*4 - 7/20*5=36/100 - 35/100=1/100
8) 37/42 - 17/24 =
37/42*4 - 17/24*7=148/168-119/168=29/168