7.
2,25•(9 11/18-7,5)-8 1/3:3 1/3=2,25
1)9 11/18-7 5/10=9 55/90-7 45/90=
2 1/9
2)2,25•2 1/9=225/100•19/9=475/100
4,75
3)8 1/3:3 1/3=25/3:10/3=5/2=2,5
4)4,75-2,5=2,25
8.
81/88•(6-1 13/15•1 19/21)=2,25
1)1 13/15•1 19/21=28/15•40/21=32/9
=3 5/9
2)6-3 5/9=5 9/9-3 5/9=2 4/9
3)81/88•2 4/9=81/88•22/9=9/4
=2,25
9.
(5 1/16-1 1/8)(5/6+3/14)=4,125
1)5 1/16-1 1/8=5 1/16-1 2/16=3 15/16
2)5/6+3/14=35/42+9/42=44/42=
1 1/21
3)3 15/16•1 1/21=63/16•22/21=33/8=
4 1/8=4,125
10.
5 1/16-1 1/8•(5/6+3/14)=3 99/112
1)5/6+3/14=35/42+9/42=44/42=1 1/21
2)1 1/8•1 1/21=9/8•22/21=33/28=
1 5/28
3)5 1/16-1 5/28=5 7/112-1 20/112=
3 99/112
11.
4/5+4/493•(7 11/12+5 7/9)=41/45
1)7 11/12+5 7/9=7 33/36+5 28/36=
12 61/36=13 25/36
2)4/493•13 25/36=4/493•493/36=
1/9
3)4/5+1/9=36/45+5/45=41/45
12.
(4/5+4/7)•(3 3/8+2 11/14)=12 138/245
1)4/5+4/7=28/35+20/35=48/35=
1 13/35
2)3 3/8+2 11/14=3 21/56+2 44/56=
5 65/56=6 9/56
3)1 13/35•6 9/56=48/35•513/56=
3078/245=12 138/245
13.
(8-2 1/7•3 1/9)•27/44=9/11
1)2 1/7•3 1/9=15/7•28/9=20/3=6 2/3
2)8-6 2/3=7 3/3-6 2/3=1 1/3
3)1 1/3•27/44=4/3•27/44=9/11
14.
(2 13/48+2 5/12):3 3/4-9 3/4:12=7/16
1)2 13/48+2 5/12=2 13/48+2 20/48=
4 33/48=4 11/16
2)4 11/16:3 3/4=75/16:15/4=5/4=1 1/4
3)9 3/4:12=39/4:12/1=39/48
4)1 1/4-39/48=1 12/48-39/48=21/48
=7/16
15.
(4 3/4-2):33/2+1 6/11:17/8=59/66
1)4 3/4-2=2 3/4
2) 2 3/4: 33/2=11/4:33/2=1/6
3)1 6/11:17/8=17/11:17/8=8/11
4)1/6+8/11=11/66+48/66=59/66