1. 19分之7×13＋19分之13×31 2.（51分之2＋18分之5）×9×17 3.（24分之5＋12分之7-3分之2）×48

1.
(7×13)/19＋(13×31)/19
=(7×13+31×13)/19
=13×(7+31)/19
=13×38/19
=13×2
=26

2.
（2/51＋5/18)×9×17
=2×9×17/51 +5×9×17/18
=18/3 +5×17/2
=6 +85/2
=97/2

3.
（5/24＋7/12-2/3）×48
=5×48/24 +7×48/12 -2×48/3
=5×2+7×4-2×16
=10+28-32
=6

1解：原式=7/19x13+13/19x31
=(7x13+13x31)/19
=13x(7+31)/19
=13x2
=26
2解：原式=(2/51+5/18)x9x17
=2x9x17/51+5x9x17/18
=2x9/3+5x17/2
=6+85/2
=97/2
=48.5
3解：原式=(5/24+7/12-2/3)x48
=5x48/24+7x48/12-2x48/3
=10+28-32
=6