數學知識交流 － 驗證答案

題目：

「Polly went to buy bottles of milk and mangoes , she went to buy 3 bottles of milk and 4 mangoes . However , she had only $77 in her purse and she hadn't enough money . The next day , she went to buy the same number of bottles of milk and mangoes with unchanged price , she had $8 more than last day , she could pay for 3 bottles of milk and 4 mangoes with $6 remained . It is known that the price of a mango is $16 less than 2 times of the price of a bottle of milk . Find the total price of 10 bottles of milk and 13 mangoes .」

Mr.A 回答了這條問題，但他的回答有很多問題 ( 漏寫、重寫、錯寫等 )，有 15 個錯處，他的回答如下：

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Lt the price of a bottle of milk is $x , then the price of a mango be (2x-16) . Then ,

3x + 4(2x-16) = 85 - 6
3x + 4(2x-16) = 79
3x + 8x - 16 = 79
10x - 64 = 79
11x + 64 = 79 + 64
11x = 143
x = 143/11
x = 13

The price of a mangoes is :

2(13) - 16
= 26 - 10
= 10

The total price of 10 bottles of milk and 13 mangoes is :

10(13) + 13(10)
= 130 + 13
= $260

Answer : The total price of 10 bottle of milk and 13 mango is 260 .

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(1) 指出所有的錯處，並
(2) 更正它們。