1) 11,25 - 3 (5/12 ) + 4,3 - 7 ( 19/30 ) = 15,55 - 3 ( 25/60 ) - 7 ( 38/60 ) =
= 15,55 - 10 ( 63/60 ) = 15,55 - 11 ( 1/20 ) = 15,55 - 11,05 = 4,5
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2) 7 ( 7/12 ) - 5 ( 5/6 ) = 7 ( 35/60 ) - 5 ( 50/60 ) = 6 ( 95/60 ) - 5 ( 50/60 ) =
= 1 ( 45/60 ) = 1,75
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3) 4,5 : 1,75 = 9/2 : 7/4 = 18/7 = 2 ( 4/7 )
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Ответ две целых четыре седьмых