(1)19
7
8 ×7,
=(19+
7
8 )×7,
=19×7+
7
8 ×7,
=133+
49
8 ,
=139
1
8 ;
(2)2.8× 1
3
4 +7
1
5 × 1
3
4 ,
=(2.8+7
1
5 )× 1
3
4 ,
=(2.8+7.2)× 1
3
4 ,
=10×
7
4 ,
=
35
2 ;
(3)
7
13 ×0.91×
2
7 ,
=(
7
13 ×
2
7 )×0.91,
=
2
13 ×0.91,
=0.14;
(4)
5
8 +
3
8 ×
2
15 ,
=
5
8 +
1
20 ,
=
27
40 ;
(5)(
7
18 +
5
27 )×
9
35 ,
=
7
18 ×
9
35 +
5
27 ×
9
35 ,
=
1
10 +
1
21 ,
=
31
210 ;
(6)
97
100 ×99,
=
97
100 ×(100-1),
=
97
100 ×100-
97
100 ×1,
=97-
97
100 ,
=96
3
100 .