2.87+5.6-0.87+4.4 11/18×9-11/18×6 420÷7÷6 9/10-(1/4+7/20)÷3/41/2x+3/5x=4.4 (解方程)

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2.87+5.6-0.87+4.4 11/18×9-11/18×6 420÷7÷6 9/10-(1/4+7/20)÷3/4
1/2x+3/5x=4.4 (解方程)

2.87+5.6-0.87+4.4
=(2.87-0.87)+(5.6+4.4)
=2+10
=12;
11/18×9-11/18×6
=(11/18)×(9-6)
=(11/18)×3
=11/6;
420÷7÷6
=420÷(7×6)
=420÷42
=10;
9/10-(1/4+7/20)÷3/4
=9/10-(1/4)×(4/3)-(7/20)×(4/3)
=9/10-1/3-7/15
=9/10-(5+7)/15
=9/10-12/15
=27/30-24/30
=3/30
=1/10
1/2x+3/5x=4.4 (解方程)
0.5x+0.6x=4.4;
1.1x=4.4;
x=4
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