a)
[tex]677 \ kg=667\cdot0,001 \ t=\boxed{0,677 \ t}\\\\1504 \ kg=1504\cdot0,001 \ kg=\boxed{1,504 \ t}\\\\70 \ kg=70\cdot0,001 \ t=\boxed{0,07 \ t}\\\\1 \ t \ 925 \ kg=1 \ t+925\cdot0,001 \ t=1 \ t+0,925 \ t=\boxed{1,925 \ t}\\\\6 \ t \ 7 \ kg=6 \ t+7\cdot0,001 \ t=6 \ t+0,007 \ t=\boxed{6,007 \ t}[/tex]
b)
[tex]0,379 \ t=0,379\cdot1000 \ kg=\boxed{379 \ kg}\\\\0,09 \ t=0,09\cdot1000 \ kg=\boxed{90 \ kg}\\\\0,69 \ t=0,69\cdot1000 \ kg=\boxed{690 \ kg}\\\\5,013 \ t=5,013\cdot1000 \ kg=\boxed{5013 \ kg}\\\\3 \ t \ 240 \ kg=3\cdot1000 \ kg+240 \ kg=\boxed{3240 \ kg}[/tex]