(7.4-2.79)+(12.6-2.21)怎样简便计算

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(7.4-2.79)+(12.6-2.21)怎样简便计算

(7.4+12.6)-(2.79+2.21)=15

(7.4+12.6)-(2.79+2.21)
20-5
15

(7.4-2.79)+(12.6-2.21)
=7.4-2.79+12.6-2.21
=(7.4+12.6)-(2.79+2.21)
=20-5
=5