1.（＋7）＋（＋3） 2.（＋7）＋（-3) 3.(＋7）＋（-7）

1.（＋7）＋（＋3）=7+3=10
2.（＋7）＋（-3)=7-3=4
3.(＋7）＋（-7）=7-7=0
We can find the rule: if the plus sign in brackets doesn't exist, the minus sign in brackets will be retained and the plus sign before the minus sign will be removed

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