a: \(2\cdot53\cdot12+4\cdot6\cdot87-3\cdot8\cdot40\)
\(=24\left(53+87-40\right)\)
=2400
b: \(5\cdot7\cdot77+7\cdot60+49\cdot25-45\cdot42\)
\(=35\cdot77+35\cdot12+49\cdot25-45\cdot42\)
\(=35\cdot89+35\left(7\cdot5-9\cdot6\right)\)
\(=35\cdot70=2450\)
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a) 2.53.12+4.6.87-3.8.40
=24.53+24.87-24.40
=24.(53+87-40)
=24.100
=2400
b) 5.7.77-7.60+49.25-45.42
=5.7.77-7.60+7.7.25-45.6.7
=7.(5.77-60+7.25-6.45)
=7.230
=1610
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