(821+345)-245=821+(345-245)=821+100=921
972-(72+888)=(972-72)+888=900-888=12
(707+432)-132=707+(432-132)=707+300=1007
906-(306+123)=(906-306)+123=600+123=723
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= ( 4 * 1,5 ) * ( 10 ^ - 3 * 10 ^ 4 ) = 6 * 10 ^ ( - 3 + 4 ) = 6 * 10 = 60
200км/200000=20000000cм/200000=100см
ответ 100см