Very easy!  The answer is obviously 75.  Here's why:

(a)  6x5=30, substitute in the quadratic expression:






then divide by -210, get 41

(b)  7+2=9, substitute in the quadratic expression:






then divide by -210, get 51

(c)  2+2=4, substitute in the quadratic expression:






then divide by -210, get 2

(d)  5x5=25, substitute in the quadratic expression:






then divide by -210, get 75

Simple, huh?  Perfectly logical!  J  

Edwin

In this problem, they want you find the result of the operation " 5×5 ".

As the base, we will use the given operation 6×5 = 41.


    +---------------------------------------------------------------+
    |   We will not use two other operations 7+2 = 51 , 2+2= 2,     |
    |   since they use the addition sign, while we are interested   |
    |      in the multiplication sign.  Therefore, we ignore        |
    |          7+2 = 51 , 2+2= 2, as they are irrelevant,           |
    |     and concentrate/focus on the unique operation 6×5 = 41,   |
    |           since it is only relevant to our goal.              |
    +---------------------------------------------------------------+


We notice that 6×5 = 41  produces the same output value as traditional  6 + 5 + 6*5 = 41.

So, following this notice, we interpret operation  a×b  as  traditional  a + b + ab.


Now we apply this fundamental rule to compute 5×5 = ?

We get  5×5 = 5 + 5 + 5*5 = 10 + 25 = 35.


At this point, the solution to this puzzle is complete, and we get the

       ANSWER.  ? = 35.    J