Answers

2016-06-02T19:46:52+08:00
    Let  x  be  the number
    is then multiplied by 4  =    4 x
    3 is added to the product   =  4 x + 3
     thus   4 x + 3 = 31
                 4 x =  31-3 = 28
                   x =  28/4   =  7
        so the number is    7
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2016-06-02T23:49:26+08:00
The answer is 7 because...

If the result is 31, but you added 3 to the product, it means that you have to minus 3 from the total. 31 - 3 = 28.
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