№5
(432²-568²)÷1000=(432+568)×(432-568)÷1000=1000×(-136)÷1000=-136
№6
4 4/9÷4/9=40/9÷4/9=40/9×9/4=10/1×1/1=10/1=10
№7
1,23×45,7 0,1×100
--------------- = -----------=10/1=10
12,3×0,457 1×1
№8
(4 1/4-2)×6 2/3=2 1/4×6 2/3=9/4×20/3=3/1×5/1=15/1=15
№9
(5 1/3-2)÷5/21=3 1/3÷5/21=10/3÷5/21=10/3×21/5=2/1×7/1=14/1=14
№10
(728²-26²)÷754=(728+26)×(728-26)÷754=754×702÷754=702
№11
7 3/4÷1/4=31/4÷1/4=31/4×4/1=31/1×1/1=31/1=31
№12
1,92×0,244 10×0,1
-----------------=-----------=1/1=1
0,192×2,44 1×1