题目内容
7×9+（7+8）×21+8×4=______．
7×9+（7+8）×21+8×4
=7×9+7×21+8×21+8×4
=（7×9+7×21）+（8×21+8×4）
=7×（9+21）+8×（21+4）
=7×30+8×25
=210+200
=410
故答案为：410．
=7×9+7×21+8×21+8×4
=（7×9+7×21）+（8×21+8×4）
=7×（9+21）+8×（21+4）
=7×30+8×25
=210+200
=410
故答案为：410．
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