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| 2020-09-01 11:37:42 +0200 | received badge | ● Student (source) |
| 2020-09-01 11:35:54 +0200 | asked a question | Can you solve a math problem: x+y=42, x-y=30? In page 43, math problem 1, on Math 4 Workbook, Part One, Vietnamese Education Publishing House: |
Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.