The fourteen digits of a credit card are to be written in the boxes shown above. If the sum of every three consecutive digits is 18, then the value of x is :

cannot be determined from the given information.

Explanation:

Let us assume right most two squares are a , b

Then Sum of all the squares = 18 x 4 + a + b .......... (1)

Also Sum of the squares before 7 = 18

Sum of the squares between 7, x = 18

and sum of the squares between x , 8 = 18

So Sum of the 14 squares = 18 + 7 + 18 + x + 18 + 8 + a + b...... (2)

Equating 1 and 2 we get x = 3