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A math problem. . . urgent
I'm X from Hefei No.36 Middle School.

There is a calculation error in the answer and it cannot be changed because the answer is recommended.

You can only answer from this window.

If you think it's ok, please give the score to X in Hefei No.36 Middle School.

thank you

The penultimate line is S5=4+7= 1 1.