For repair of school brought 900 pieces of the white and red bricks identical on weight. The mass of all red bricks of 1900 kg, and white - 1700 kg. Find quantity of red and white bricks separately. it is possible short record by the table I ask you

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1) 1900+1700=3600 (kg) - the mass of all bricks. 2) 3600:900=4 (kg) - the mass of 1 brick. 3) 1900:4=475-red bricks. 4) 1700:4=425-white bricks. of 1900+1700=3600 (kg) - the mass of all bricks of 3600/900=4 (kg) - weighs 1 brick 1900/4 = 475 (pieces) - red bricks of 900-475=425 (pieces) - white bricks of 1700+1900=3600 (kg) - only 3600:900=4 (kg) - 1 brick of 1900:4=475 pieces 1700:4=425 pieces weighs
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Answer add